fs: f2fs: insert space around that ':' and ', '

clean up checkpatch error:
ERROR: space required after that ':'
ERROR: space required after that ','

Signed-off-by: youngjun yoo <youngjun.willow@gmail.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>