Universal plane support had placeholders for cursor planes, but didn't
actually do anything with them.  Save the cursor plane reference inside
the crtc and update the cursor plane parameter from void* to drm_plane.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: Pallavi G<pallavi.g@intel.com>
Acked-by: NDave Airlie <airlied@linux.ie>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>