ip_tunnel: Resolve ipsec merge conflict properly.

We want to use dev_set_mtu() regardless of how we calculate
the mtu value.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_tunnel.c

@@ -1120,14 +1120,14 @@ int ip_tunnel_newlink(struct net_device *dev, struct nlattr *tb[],
 	if (tb[IFLA_MTU]) {
 		unsigned int max = 0xfff8 - dev->hard_header_len - nt->hlen;
 
-		dev->mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU,
-				 (unsigned int)(max - sizeof(struct iphdr)));
-	} else {
-		err = dev_set_mtu(dev, mtu);
-		if (err)
-			goto err_dev_set_mtu;
+		mtu = clamp(dev->mtu, (unsigned int)ETH_MIN_MTU,
+			    (unsigned int)(max - sizeof(struct iphdr)));
 	}
 
+	err = dev_set_mtu(dev, mtu);
+	if (err)
+		goto err_dev_set_mtu;
+
 	ip_tunnel_add(itn, nt);
 	return 0;