Add a small static inline helper to grab the vblank wait queue based on
the drm_crtc.
This is useful for drivers to do internal vblank waits using
wait_event() & co.
v2: Pimp commit message (Daniel)
Add kernel doc (Daniel)
Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>