f2fs: fix to update i_ctime in __f2fs_setxattr()

generic/728       - output mismatch (see /media/fstests/results//generic/728.out.bad)
    --- tests/generic/728.out	2023-07-19 07:10:48.362711407 +0000
    +++ /media/fstests/results//generic/728.out.bad	2023-07-19 08:39:57.000000000 +0000
     QA output created by 728
    +Expected ctime to change after setxattr.
    +Expected ctime to change after removexattr.
     Silence is golden
    ...
    (Run 'diff -u /media/fstests/tests/generic/728.out /media/fstests/results//generic/728.out.bad'  to see the entire diff)
generic/729        1s

It needs to update i_ctime after {set,remove}xattr, fix it.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>