loop: fix error return code in loop_add()

Fix to return a negative error code from the error handling
case, as returned elsewhere in this function.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 747bb2a..ee13a82 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1623,6 +1623,7 @@
 		goto out_free_dev;
 	i = err;
 
+	err = -ENOMEM;
 	lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
 	if (!lo->lo_queue)
 		goto out_free_dev;