BACKPORT: f2fs: use cow inode data when updating atomic write

Need to use cow inode data content instead of the one in the original
inode, when we try to write the already updated atomic write files.

Bug: 298879042
Bug: 308706939
Change-Id: I042a348e4b9ab4c4746dc02b169f500fe31f443f
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit a13c8e91)
Signed-off-by: zhoudan8 <zhoudan8@xiaomi.com>