mkfs.f2fs: fix storing volume label correctly in utf16

This patch fixes to store volume label as utf16 correctly.

Many conversion codes are copied from exfat-tools.

Change-Id: Iee96b27a5bfc4938f285b4de49d32e01a181d17f
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
4 files changed