staging: vchiq:remove unneeded flush_workqueue

All work currently pending will be done first by calling destroy_workqueue,
so there is no need to flush it explicitly.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ran jianping <ran.jianping@zte.com.cn>
Link: https://lore.kernel.org/r/20220422093340.2781311-1-ran.jianping@zte.com.cnSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/vchiq-mmal/mmal-vchiq.c

@@ -1841,7 +1841,6 @@ int vchiq_mmal_finalise(struct vchiq_mmal_instance *instance)
 	mutex_unlock(&instance->vchiq_mutex);
 
 	vchiq_shutdown(instance->vchiq_instance);
-	flush_workqueue(instance->bulk_wq);
 	destroy_workqueue(instance->bulk_wq);
 
 	idr_destroy(&instance->context_map);