f2fs: add a new mount option: inline_data

Add a mount option: inline_data. If the mount option is set,
data of New created small files can be stored in their inode.

Signed-off-by: Huajun Li <huajun.li@intel.com>
Signed-off-by: Haicheng Li <haicheng.li@linux.intel.com>
Signed-off-by: Weihong Xu <weihong.xu@intel.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>