f2fs: fix to use inline space only if inline_xattr is enable

With below mkfs and mount option:

MKFS_OPTIONS  -- -O extra_attr -O project_quota -O inode_checksum -O flexible_inline_xattr -O inode_crtime -f
MOUNT_OPTIONS -- -o noinline_xattr

We may miss xattr data with below testcase:
- mkdir dir
- setfattr -n "user.name" -v 0 dir
- for ((i = 0; i < 190; i++)) do touch dir/$i; done
- umount
- mount
- getfattr -n "user.name" dir

user.name: No such attribute

The root cause is that we persist xattr data into reserved inline xattr
space, even if inline_xattr is not enable in inline directory inode, after
inline dentry conversion, reserved space no longer exists, so that xattr
data missed.

Let's use inline xattr space only if inline_xattr flag is set on inode
to fix this iusse.

Fixes: 6afc662e ("f2fs: support flexible inline xattr size")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -2570,7 +2570,9 @@ static inline void *inline_xattr_addr(struct inode *inode, struct page *page)
 
 static inline int inline_xattr_size(struct inode *inode)
 {
+	if (f2fs_has_inline_xattr(inode))
 		return get_inline_xattr_addrs(inode) * sizeof(__le32);
+	return 0;
 }
 
 static inline int f2fs_has_inline_data(struct inode *inode)