f2fs: Update to proper 3.4 support

http://git.kernel.org/cgit/linux/kernel/git/jaegeuk/f2fs.git/log/?h=linux-3.4

Conflicts:
	fs/f2fs/f2fs.h

Change-Id: Ica17871e847d4807c7ef24ea77dd4bff5451f5c7