ext4: remove redundant sb checksum recomputation

mainline inclusion
from mainline-v5.11-rc1
commit 81414b4dd48f596bf33e1b32c2e43e2047150ca6
category: bugfix
bugzilla: 46758
CVE: NA

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Superblock is written out either through ext4_commit_super() or through
ext4_handle_dirty_super(). In both cases we recompute the checksum so it
is not necessary to recompute it after updating superblock free inodes &
blocks counters.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-3-jack@suse.cz


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>