UPSTREAM: f2fs: atomic: fix to truncate pagecache before on-disk metadata truncation

We should always truncate pagecache while truncating on-disk data.

Fixes: a46bebd5 ("f2fs: synchronize atomic write aborts")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Bug: 369150601
Change-Id: I9c98170719c3866495640739734e355c9685cb04
(cherry picked from commit ebd3309a)
Signed-off-by: Daeho Jeong <daehojeong@google.com>