Allow userptr objects to be created and used via libdrm_intel.
At the moment tiling and mapping to GTT aperture is not supported
due hardware limitations across different generations and uncertainty
about its usefulness.
v2: Improved error handling in feature detection per review comments.
v3: Rebase on top of the drm_public addition, minor whitespace addition.
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com> (v3)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> (v1,v2)
ae8edc7544