dm thin: Add missing destroy_work_on_stack()

This commit add missed destroy_work_on_stack() operations for pw->worker in
pool_work_wait().

Fixes: e7a3e87 ("dm thin: cleanup noflush_work to use a proper completion")
Cc: stable@vger.kernel.org
Signed-off-by: Yuan Can <yuancan@huawei.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

drivers/md/dm-thin.c

@@ -2484,6 +2484,7 @@ static void pool_work_wait(struct pool_work *pw, struct pool *pool,
 	init_completion(&pw->complete);
 	queue_work(pool->wq, &pw->worker);
 	wait_for_completion(&pw->complete);
+	destroy_work_on_stack(&pw->worker);
 }
 
 /*----------------------------------------------------------------*/