!4057 ext4: correct return value of ext4_convert_meta_bg

Merge Pull Request from: @ci-robot 
 
PR sync from: Baokun Li <libaokun1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/24P3K6JYSJFEKUZMV2XJHTFTW24TIC4Q/ 
 
https://gitee.com/openeuler/kernel/issues/I853YM 
 
Link:https://gitee.com/openeuler/kernel/pulls/4057

 

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