workqueue: cosmetic update in rescuer_thread()

rescuer_thread() caches &rescuer->scheduled in a local variable
scheduled for convenience.  There's one WARN_ON_ONCE() which was using
&rescuer->scheduled directly.  Replace it with the local variable.

This patch causes no functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -2248,7 +2248,7 @@ static int rescuer_thread(void *__rescuer)
 		 * Slurp in all works issued via this workqueue and
 		 * process'em.
 		 */
-		WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
+		WARN_ON_ONCE(!list_empty(scheduled));
 		list_for_each_entry_safe(work, n, &pool->worklist, entry)
 			if (get_work_pwq(work) == pwq)
 				move_linked_works(work, scheduled, &n);