!1427 nbd: Fix debugfs_create_dir error checking

Merge Pull Request from: @ci-robot 
 
PR sync from: Zhong Jinghua <zhongjinghua@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/CXCW33MDQZLHTCOH6HEFOVC5GK2Y4TCX/ 
 
https://gitee.com/openeuler/kernel/issues/I7FF4R 
 
Link:https://gitee.com/openeuler/kernel/pulls/1427

 

Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>