ext4: use sbi instead of EXT4_SB(sb) in ext4_update_super()

mainline inclusion
from mainline-v5.11-rc4
commit e92ad03f
category: bugfix
bugzilla: 50839
CVE: NA

-----------------------------------------------

No behavioral change.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201216101844.22917-6-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: Zheng Zengkai <zhengzengkai@huawei.com>