datapath: Print device when warning about over MTU packets.

If an attempt is made to transmit a packet that is over the device's
MTU then we log it using the datapath's name.  However, it is much
more helpful to use the device name instead.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Kyle Mestery <kmestery@cisco.com>

datapath/vport-netdev.c

@@ -304,7 +304,7 @@ static int netdev_send(struct vport *vport, struct sk_buff *skb)
 
 	if (unlikely(packet_length(skb) > mtu && !skb_is_gso(skb))) {
 		net_warn_ratelimited("%s: dropped over-mtu packet: %d > %d\n",
-				     ovs_dp_name(vport->dp),
+				     netdev_vport->dev->name,
 				     packet_length(skb), mtu);
 		goto error;
 	}