Overlayfs should print an error message if an incorrect mount option
is caught like other filesystems.

After this patch, improper option input could be clearly known.
Reported-by: Fabian Sturm <fabian.sturm@aduu.de>
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>