BACKPORT: f2fs: replace F2FS_I(inode) and sbi by the local variable

We have define 'fi' at the begin of the functions, just use it,
rather than use F2FS_I(inode) again.

Bug: 298879042
Change-Id: Id5565572e72793deb7f7c6311ec28cdb0a4e7da8
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
[Jaegeuk Kim: replace sbi]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 9fd22b27)
Signed-off-by: zhoudan8 <zhoudan8@xiaomi.com>