vxlan: fix error return code in __vxlan_dev_create()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 0ce1822c ("vxlan: add adjacent link to limit depth level")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NZhang Changzhong <zhangchangzhong@huawei.com>
Link: https://lore.kernel.org/r/1606903122-2098-1-git-send-email-zhangchangzhong@huawei.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

drivers/net/vxlan.c

@@ -3880,8 +3880,10 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
 
 	if (dst->remote_ifindex) {
 		remote_dev = __dev_get_by_index(net, dst->remote_ifindex);
-		if (!remote_dev)
+		if (!remote_dev) {
+			err = -ENODEV;
 			goto errout;
+		}
 
 		err = netdev_upper_dev_link(remote_dev, dev, extack);
 		if (err)