fs: f2fs: Convert direct_IO to use iov_iter

Change-Id: I3c7c527c5e3ce55a39d1afd41e62954471385b0a
Signed-off-by: Evisceration <eviscerationls@gmail.com>
enable f2fs, regenerate defconfig

Change-Id: Id117308abd9905204195110f455451221447e5b8