f2fs: compress: fix to guarantee persisting compressed blocks by CP

If data block in compressed cluster is not persisted with metadata
during checkpoint, after SPOR, the data may be corrupted, let's
guarantee to write compressed page by checkpoint.

Fixes: 4c8ff709

 ("f2fs: support data compression")
Reviewed-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>