f2fs: clean up with F2FS_BLK_ALIGN

Clean up F2FS_BYTES_TO_BLK(x + F2FS_BLKSIZE - 1) with F2FS_BLK_ALIGN(x).

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>