f2fs: update i_flags correctly

f2fs enables hash-indexed directory by default, so we need to tag
FS_INDEX_FL in inode::i_flags during directory creataion, in order
to show correct status of inode in lsattr:

Before:
------------------- /mnt/f2fs/dir/
After:
-----------I------- /mnt/f2fs/dir/
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/namei.c

@@ -100,6 +100,9 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
 	F2FS_I(inode)->i_flags =
 		f2fs_mask_flags(mode, F2FS_I(dir)->i_flags & F2FS_FL_INHERITED);
 
+	if (S_ISDIR(inode->i_mode))
+		F2FS_I(inode)->i_flags |= FS_INDEX_FL;
+
 	if (F2FS_I(inode)->i_flags & FS_PROJINHERIT_FL)
 		set_inode_flag(inode, FI_PROJ_INHERIT);