fs: import f2fs from git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git (branch dev)

Up-to-date with
git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git @48af90425ce96078530f1ff01d482cad12005b7e
(f2fs: introduce -o fastboot for reducing booting time only)

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
squash commit 1-f2fs support
Makefile: remove -w flag
gitignore updated
fs: default to noatime/nodiratime
fs: import f2fs from git://git.kernel.org/pub/scm/linux/kernel/git/ja…
selinux: whitelist f2fs
afsync: extend to f2fs