mkfs.f2fs: 512 UTF-16 characters for label
mkfs.f2fs: 512 UTF-16 characters for label

We can use 512 UTF-16 characters for label.

Change-Id: I8f6a5628049582aa0c89b9ef812c8c7a12fe70ee
Signed-off-by: Jaegeuk Kim <71255387a32c360dfbe6dfb7aaeb123bf1dc8cb6@kernel.org>

TeamTwisted/android_external_f2fs-tools,TeamTwisted/android_external_f2fs-tools