MFC 297776,297777,297779: Add DDB commands to cxgbe(4).

297776:
Add a function to lookup a device_t object by name.

This just walks the global list of devices looking for one with the
requested name. The one use case outside of devctl2's implementation
is for DDB commands that wish to lookup devices by name.

297777:
Add a 'show t4 tcb <nexus> <tid>' command to dump a TCB from DDB.

This allows the contents of a TCB to be extracted from a T4/T5 card in
DDB after a panic.

297779:
Add a 'show t4 devlog <nexus>' DDB command.

This command displays the adapter's firmware device log similar to the
dev.<nexus>.misc.devlog sysctl.

Sponsored by: Chelsio Communications

MFC 305034: Implement 'devctl clear driver' to undo a previous 'set driver'.

Add a new 'clear driver' command for devctl along with the accompanying
ioctl and devctl_clear_driver() library routine to reset a device to
use a wildcard devclass instead of a fixed devclass. This can be used
to undo a previous 'set driver' command. After the device's name has
been reset to permit wildcard names, it is reprobed so that it can
attach to newly-available (to it) device drivers.

Sponsored by: Chelsio Communications

MFC 278320,278336,278830,285621:
Add devctl(8): a utility for manipulating new-bus devices. Note that
this version does not include the 'suspend' and 'resume' commands
present in HEAD as those depend on larger changes to the suspend and
resume code in the kernel.

278320:
Add a new device control utility for new-bus devices called devctl. This
allows the user to request administrative changes to individual devices
such as attach or detaching drivers or disabling and re-enabling devices.
- Add a new /dev/devctl2 character device which uses ioctls for device
requests. The ioctls use a common 'struct devreq' which is somewhat
similar to 'struct ifreq'.
- The ioctls identify the device to operate on via a string. This
string can either by the device's name, or it can be a bus-specific
address. (For unattached devices, a bus address is the only way to
locate a device.) Bus drivers register an eventhandler to claim
unrecognized device names that the driver recognizes as a valid address.
Two buses currently support addresses: ACPI recognizes any device
in the ACPI namespace via its full path starting with "\" and
the PCI bus driver recognizes an address specification of
'pci[<domain>:]<bus>:<slot>:<func>' (identical to the PCI selector
strings supported by pciconf).
- To make it easier to cut and paste, change the PnP location string
in the PCI bus driver to output a full PCI selector string rather
than 'slot=<slot> function=<func>'.
- Add a devctl(3) interface in libdevctl which provides a wrapper around
the ioctls and is the preferred interface for other userland code.
- Add a devctl(8) program which is a simple wrapper around the requests
supported by devctl(3).
- Add a resource_unset_value() function that can be used to remove a
hint from the kernel environment. This is used to clear a
hint.<driver>.<unit>.disabled hint when re-enabling a boot-time
disabled device.

278336:
Unbreak the build (memchr is explicitly required by devctl(9) after r278320)

278830:
install the man page...

285621:
Fix formatting.

Approved by: re (marius)

MFC r271889, 272799, 272800, 274976
This brings in bus_get_domain() and the related reporting via devinfo,
dmesg, and sysctl.

Obtained from: adrian, jhb
Sponsored by: Netflix, Inc.

MFC r269594, r269596, r269597, r269598, r269605, r269606:

Set ofwbus and simplebus to attach during BUS_PASS_BUS.

Define names that drivers can use to adjust their position relative to
other drivers within a BUS_PASS

Adjust ofwbus and simplebus to attach at BUS_PASS_ORDER_MIDDLE, so that
a platform can attach some other bus first if necessary.

Set the pl310 L2 cache driver to attach during the middle of BUS_PASS_CPU.

Attach arm generic interrupt and timer drivers in the middle of
BUS_PASS_INTERRUPT and BUS_PASS_TIMER, respectively.

Add an arm option, ARM_DEVICE_MULTIPASS, used to opt-in to multi-pass
device attachment on arm platforms. If this is defined, nexus attaches
early in BUS_PASS_BUS, and other busses and devices attach later, in the
pass number they are set up for. Without it defined, nexus attaches in
BUS_PASS_DEFAULT and thus so does everything else, which is status quo.

MFC r271889, 272799, 272800, 274976
This brings in bus_get_domain() and the related reporting via devinfo,
dmesg, and sysctl.

Obtained from: adrian, jhb
Sponsored by: Netflix, Inc.

MFC r269594, r269596, r269597, r269598, r269605, r269606:

Set ofwbus and simplebus to attach during BUS_PASS_BUS.

Define names that drivers can use to adjust their position relative to
other drivers within a BUS_PASS

Adjust ofwbus and simplebus to attach at BUS_PASS_ORDER_MIDDLE, so that
a platform can attach some other bus first if necessary.

Set the pl310 L2 cache driver to attach during the middle of BUS_PASS_CPU.

Attach arm generic interrupt and timer drivers in the middle of
BUS_PASS_INTERRUPT and BUS_PASS_TIMER, respectively.

Add an arm option, ARM_DEVICE_MULTIPASS, used to opt-in to multi-pass
device attachment on arm platforms. If this is defined, nexus attaches
early in BUS_PASS_BUS, and other busses and devices attach later, in the
pass number they are set up for. Without it defined, nexus attaches in
BUS_PASS_DEFAULT and thus so does everything else, which is status quo.