Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Rename the 'M_B' macro in t4_regs.h to 'CXGBE_M_B'.

This fixes a conflict with the M_B macro in powerpc's
<machine/db_machdep.h> exposed by the recent addition of DDB commands
to the cxgbe driver.

Discussed with: np
Reported by: bz
Sponsored by: Chelsio Communications

cxgbe: catch up with the latest hardware-related definitions.

Obtained from: Chelsio Communications
Sponsored by: Chelsio Communications

Add new a M_START() mbuf macro that returns a pointer to the start of
an mbuf's storage (internal or external).

Add a new M_SIZE() mbuf macro that returns the size of an mbuf's
storage (internal or external).

These contrast with m_data and m_len, which are with respect to data
in the buffer, rather than the buffer itself.

Rewrite M_LEADINGSPACE() and M_TRAILINGSPACE() in terms of M_START()
and M_SIZE().

This is done as we currently have many instances of using mbuf flags
to generate pointers or lengths for internal storage in header and
regular mbufs, as well as to external storage. Rather than replicate
this logic throughout the network stack, centralising the
implementation will make it easier for us to refine mbuf storage.
This should also help reduce bugs by limiting the amount of
mbuf-type-specific pointer arithmetic. Followup changes will
propagate use of the macros throughout the stack.

M_SIZE() conflicts with one macro in the Chelsio driver; rename that
macro in a slightly unsatisfying way to eliminate the collision.

MFC after: 3 days
Obtained from: jeff (with enhancements)
Sponsored by: EMC / Isilon Storage Division
Reviewed by: bz, glebius, np
Differential Revision: https://reviews.freebsd.org/D753

cxgbe(4): Add support for Chelsio's Terminator 5 (aka T5) ASIC. This
includes support for the NIC and TOE features of the 40G, 10G, and
1G/100M cards based on the T5.

The ASIC is mostly backward compatible with the Terminator 4 so cxgbe(4)
has been updated instead of writing a brand new driver. T5 cards will
show up as cxl (short for cxlgb) ports attached to the t5nex bus driver.

Sponsored by: Chelsio

cxgbe(4) - NIC driver for Chelsio T4 (Terminator 4) based 10Gb/1Gb adapters.

MFC after: 3 weeks