f2fs: introduce cur_cp_version function to reduce code size

This patch introduces a new inline function, cur_cp_version, to reduce redundant
codes.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

diff --cc fs/f2fs/checkpoint.c
Simple merge

diff --cc fs/f2fs/f2fs.h
Simple merge

diff --cc fs/f2fs/file.c
Simple merge

diff --cc fs/f2fs/recovery.c
Simple merge

diff --cc fs/f2fs/xattr.c
Simple merge