ax88172a: fix ax88172a_unbind() failures

If ax88172a_unbind() fails, make sure that the return code is
less than zero so that cleanup is done properly and avoid UAF.

Fixes: a9a51bd ("ax88172a: fix information leak on short answers")
Signed-off-by: George Kennedy <george.kennedy@oracle.com>
Reported-by: syzbot+4cd84f527bf4a10fc9c1@syzkaller.appspotmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/ax88172a.c

@@ -187,6 +187,7 @@ static int ax88172a_bind(struct usbnet *dev, struct usb_interface *intf)
 	ret = asix_read_cmd(dev, AX_CMD_READ_NODE_ID, 0, 0, ETH_ALEN, buf, 0);
 	if (ret < ETH_ALEN) {
 		netdev_err(dev->net, "Failed to read MAC address: %d\n", ret);
+		ret = -EIO;
 		goto free;
 	}
 	memcpy(dev->net->dev_addr, buf, ETH_ALEN);