drm crtc: add forgotten idr cleanup functions

drm_mode_config_init initializes the idr with idr_init, so
add the missing counterparts in drm_mode_config_cleanup.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_crtc.c

@@ -1048,6 +1048,9 @@ void drm_mode_config_cleanup(struct drm_device *dev)
 				 head) {
 		plane->funcs->destroy(plane);
 	}
+
+	idr_remove_all(&dev->mode_config.crtc_idr);
+	idr_destroy(&dev->mode_config.crtc_idr);
 }
 EXPORT_SYMBOL(drm_mode_config_cleanup);