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: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1623,6 +1623,7 @@ static int loop_add(struct loop_device **l, int i)
 		goto out_free_dev;
 	i = err;
 
+	err = -ENOMEM;
 	lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
 	if (!lo->lo_queue)
 		goto out_free_dev;