drm/radeon: Add RADEON_INFO_VA_UNMAP_WORKING query
This tells userspace that it's safe to use the RADEON_VA_UNMAP operation
of the DRM_RADEON_GEM_VA ioctl.
Cc: stable@vger.kernel.org
(NOTE: Backporting this commit requires at least backports of commits
a4c9d6a16f37a2b20617e2f48a2ec6db85ccfd4a,
3dde123fa18de2b6e2862b687065ead65d1757ea and
ada50f6365a32f79090c2f279b6be45af5ecebfb as well, otherwise using
RADEON_VA_UNMAP runs into trouble)
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>