commit fc0065ad upstream.

There exists almost same codes when get the value of pre_version
and cur_version in function validate_checkpoint, this patch adds
get_checkpoint_version to clean up redundant codes.
Signed-off-by: Tiezhu Yang <kernelpatch@126.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[bwh: Backported to 4.4: f2fs_crc_valid() doesn't take an f2fs_sb_info pointer]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>