[syzbot] WARNING: kobject bug in erofs_unregister_sysfs

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+f05ba4652c0471416eaf at syzkaller.appspotmail.com

Tested on:

commit:         a1108dcd erofs: rename ctime to mtime
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev
kernel config:  https://syzkaller.appspot.com/x/.config?x=442f8ac61e60a75e
dashboard link: https://syzkaller.appspot.com/bug?extid=f05ba4652c0471416eaf
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.