[PATCH] remove the test for null waitqueue in __wake_up()

I've had a warning in there for 4-5 months and it has never triggered.  I
think it's safe to remove this test.

kernel/sched.c

@@ -1427,9 +1427,6 @@ void __wake_up(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
 {
 	unsigned long flags;
 
-	if (unlikely(!q))
-		return;
-
 	spin_lock_irqsave(&q->lock, flags);
 	__wake_up_common(q, mode, nr_exclusive, 0);
 	spin_unlock_irqrestore(&q->lock, flags);