blk-throttle: use queue_is_locked() instead of lockdep_is_held()

We can't use the latter if !CONFIG_LOCKDEP.

Reported-by: Sedat Dilek <sedat.dilek@googlemail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-throttle.c

@@ -1218,7 +1218,7 @@ void blk_throtl_drain(struct request_queue *q)
 	struct bio_list bl;
 	struct bio *bio;
 
-	lockdep_is_held(q->queue_lock);
+	WARN_ON_ONCE(!queue_is_locked(q));
 
 	bio_list_init(&bl);