DRM removal soon

[Warner Losh]

The parts of drm that we're removing are up for review:
https://reviews.freebsd.org/D19196

Since the drm-legacy-kmod or the drm-kmod packages seem to be stable and
working well for most people, the time has come to finish the removal of
most of the drm code in FreeBSD.

The intel and radeon drivers will be removed. The ability to build things
as a module will be removed. Some bits will remain for the TEGRA arm board,
since the transition from the drm code base isn't as straight forward as it
was for the intel and amd drivers (the effort to emulate the kernel
environment on arm is significantly higher than x86 because in addition to
programming to the GPU, clocks, power regulators, etc need to be programmed
as well. The interfaces here are not standardized and different greatly
between FreeBSD and Linux).

Absent any significant last minute issue, it is my intention to commit this
change on Feb 21st, which is 20 days later than had been previously
announced.

Warner