drm/udl: Drop drm_vblank_cleanup

udl doesn't shut down the display, so stopping the vblank isn't going
to do much good either. Just drop it.

Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170621082850.13224-11-daniel.vetter@ffwll.ch

drivers/gpu/drm/udl/udl_main.c

@@ -371,8 +371,6 @@ void udl_driver_unload(struct drm_device *dev)
 {
 	struct udl_device *udl = dev->dev_private;
 
-	drm_vblank_cleanup(dev);
-
 	if (udl->urbs.count)
 		udl_free_urb_list(dev);