This will allow __drm_mode_object_file to be extended to perform
access control checks based on the file in use.

v2: Also fix up vboxvideo driver in staging

[airlied: merging early as this is an API change]
Suggested-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>