LinuxKPI: Remove sys/rman.h include from LKPI headers.

sys/rman.h defines `resource` structure which conflicts with the Linux
structure of the same name. To fix that remove reference to sys/rman.h
from linux/pci.h and move resource management code to linux_pci.c.
Update consumers which were depending on linux/pci.h pollution.

No functional changes intended.

Sponsored by: Serenity Cyber Security, LLC
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D42792

Revert "linuxkpi: `GFP_KERNEL` equals `M_NOWAIT` now"

This change seems to break some drivers such as the mlx5*(4) drivers.

As kib@ says:
> According to the 'official' Linux kernel documentation, the GFP_KERNEL
> flag implies sleepable context.

It was introduced while working on the new vt(4)/DRM integration [1].
During this work, doing sleepable allocations broke vt(4) and the DRM
drivers. However, I made further improvements and some locking-related
fixed to the new integration without revisiting the need for it.

After more testing, the improvements to the integration mentionned above
seems to make the change to `GFP_KERNEL` unneeded now. I can thus
revert it to restore expectations of other drivers.

This reverts commit 14dcd40983748596d116d91acb934a8a95ac76bc.

[1] https://github.com/freebsd/drm-kmod/pull/243

Reviewed by: kib
Approved by: kib
Differential Revision: https://reviews.freebsd.org/D42962

linuxkpi: `GFP_KERNEL` equals `M_NOWAIT` now

... instead of `M_WAITOK`.

[Why]
The reason is that in some places in the DRM drivers (in particular, the
framebuffer management code), kmalloc() is called from a non-sleepable
context, such as after a call to mtx_lock(8) with an MTX_DEF mutex.

If `GFP_KERNEL` is defined as `M_WAITOK`, we hit an assertion from
witness(4).

[How]
The definition of `GFP_KERNEL` is changed to `M_NOWAIT`. This means that
callers should verify the return value of kmalloc(). Fortunately, this
is always the case in Linux.

Reviewed by: bz, emaste, manu
Approved by: manu
Differential Revision: https://reviews.freebsd.org/D42054

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

LinuxKPI: Hide some internal symbols in linux_interrupt.c

Reviewed by: hselasky, manu
Differential revision: https://reviews.freebsd.org/D32168

LinuxKPI: Remove FreeBSD struct resource from all LKPI headers

except linux/pci.h to avoid conflicts with Linux version.
This allows to #define resource in drm-kmod globally and strip some #ifdef-s

Reviewed by: hselasky, manu
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D31673