drm: Remove some unused stuff from drm_plane

There's a bunch of unused members inside drm_plane, bloating the size of
the structure needlessly. Eliminate them.

v2: Remove all of it from kernel-doc too

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 755d9bb..c9f9f3d 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1805,7 +1805,7 @@
 
 	plane_resp->plane_id = plane->base.id;
 	plane_resp->possible_crtcs = plane->possible_crtcs;
-	plane_resp->gamma_size = plane->gamma_size;
+	plane_resp->gamma_size = 0;
 
 	/*
 	 * This ioctl is called twice, once to determine how much space is