Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

drm/radeon: Import the Radeon KMS driver

This driver is based on Linux 3.8 and a previous effort by kan@.

More informations about this project can be found on the FreeBSD wiki:
https://wiki.freebsd.org/AMD_GPU

The driver is split into:

sys/dev/drm2:
The driver sources.

sys/modules/drm2/radeonkmw:
The driver main kernel module's Makefile.

sys/modules/drm2/radeonkmsfw:
All firmware kernel module Makefiles. There's one directory and one
Makefile for each firmware.

sys/contrib/dev/drm2/radeonkmsfw:
All firmware binary sources.

tools/tools/drm/radeon
Tools to update firmwares or regenerate some headers.

Merging the driver to FreeBSD 9.x may be possible but not a priority for
now.

Help from: kib@, kan@
Tested by: avg@, kwm@, ray@,
Alexander Yerenkow <yerenkow@gmail.com>,
Anders Bolt-Evensen <andersbo87@me.com>,
Denis Djubajlo <stdedjub@googlemail.com>,
J.R. Oldroyd <fbsd@opal.com>,
Mikaël Urankar <mikael.urankar@gmail.com>,
Pierre-Emmanuel Pédron <pepcitron@gmail.com>,
Sam Fourman Jr. <sfourman@gmail.com>,
Wade <wade-is-great@live.com>,
(probably other I forgot...)
HW donations: kyzh, Yakaz

drm: Update drm_pciids.h based on Linux 3.8

This header can be easily updated using the new "gen-drm_pciids" script,
available in tools/tools/drm. The script uses the Linux' drm_pciids.h
header for new IDs, the FreeBSD's one because we add the name of the
device to each IDs, and the PCI IDs database (misc/pciids port) to fill
this name automatically for new IDS.

To call the script:
tools/tools/drm/gen-drm_pciids \
/path/to/linux/drm_pciids.h \
/path/to/freebsd/drm_pciids.h \
/path/to/pciids/pci.ids