block: don't remove hctx debugfs dir from blk_mq_exit_queue

The queue's top debugfs dir is removed from blk_release_queue(), so all
hctx's debugfs dirs are removed from there. Given blk_mq_exit_queue()
is only called from blk_cleanup_queue(), it isn't necessary to remove
hctx debugfs from blk_mq_exit_queue().

So remove it from blk_mq_exit_queue().
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220308055200.735835-11-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -3462,7 +3462,6 @@ static void blk_mq_exit_hw_queues(struct request_queue *q,
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (i == nr_queue)
 			break;
-		blk_mq_debugfs_unregister_hctx(hctx);
 		blk_mq_exit_hctx(q, set, hctx, i);
 	}
 }