f2fs: clean up f2fs_sb_has_xxx functions

This patch introduces F2FS_FEATURE_FUNCS to clean up the definitions of
different f2fs_sb_has_xxx functions.

Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>