Now we don't need to be too much careful about storage alignment for dio, since
its speed becomes quite fast and we'd better avoid any misalignment first.

Revert: 38aa0889 (f2fs: align direct_io'ed data to section)
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>