workqueue: use schedule_timeout_interruptible() instead of open code

schedule_timeout_interruptible(CREATE_COOLDOWN) is exactly the same as
the original code.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -1917,8 +1917,7 @@ restart:
 		if (!need_to_create_worker(pool))
 			break;
 
-		__set_current_state(TASK_INTERRUPTIBLE);
-		schedule_timeout(CREATE_COOLDOWN);
+		schedule_timeout_interruptible(CREATE_COOLDOWN);
 
 		if (!need_to_create_worker(pool))
 			break;