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

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

LinuxKPI: cache.h add L1_CACHE_ALIGN()

Sponsored by: The FreeBSD Foundation
MFC after: 7 days
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D36655

LinuxKPI: Constantly use _LINUXKPI_ prefix in include guards

MFC after: 1 week
Reviewed by: bz, emaste, hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33562

LinuxKPI: cache.h add SMP_CACHE_BYTES

Add a definition for SMP_CACHE_BYTES and while here include sys/param.h
for CACHE_LINE_SIZE as otherwise code might not compile standalone.

Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D30419

Finish process of moving the LinuxKPI module into the default kernel build.

- Move all files related to the LinuxKPI into sys/compat/linuxkpi and
its subfolders.
- Update sys/conf/files and some Makefiles to use new file locations.
- Added description of COMPAT_LINUXKPI to sys/conf/NOTES which in turn
adds the LinuxKPI to all LINT builds.
- The LinuxKPI can be added to the kernel by setting the
COMPAT_LINUXKPI option. The OFED kernel option no longer builds the
LinuxKPI into the kernel. This was done to keep the build rules for
the LinuxKPI in sys/conf/files simple.
- Extend the LinuxKPI module to include support for USB by moving the
Linux USB compat from usb.ko to linuxkpi.ko.
- Bump the FreeBSD_version.
- A universe kernel build has been done.

Reviewed by: np @ (cxgb and cxgbe related changes only)
Sponsored by: Mellanox Technologies