drm/vgaarb: add VGA arbitration support to the drm and kms.
VGA arb requires DRM support for non-kms drivers, to turn on/off irqs when disabling the mem/io regions. VGA arb requires KMS support for GPUs where we can turn off VGA decoding. Currently we know how to do this for intel and radeon kms drivers, which allows them to be removed from the arbiter. This patch comes from Fedora rawhide kernel. Signed-off-by: Dave Airlie <email@example.com>