blk-mq: free hctx->ctx_map when init failed

Avoid memory leak in the failure path.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ee225cc..5fbbb22 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1289,6 +1289,7 @@
 
 		blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
 		kfree(hctx->ctxs);
+		kfree(hctx->ctx_map);
 	}
 
 	return 1;