macvlan: play well with ipvlan device

If device is already used as an ipvlan port then refuse to
use it as a macvlan port at early stage of port creation.

	thost1:~# ip link add link eth0 ipvl0 type ipvlan
	thost1:~# echo $?
	0
	thost1:~# ip link add link eth0 mvl0 type macvlan
	RTNETLINK answers: Device or resource busy
	thost1:~# echo $?
	2
	thost1:~#

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -1057,6 +1057,9 @@ static int macvlan_port_create(struct net_device *dev)
 	if (dev->type != ARPHRD_ETHER || dev->flags & IFF_LOOPBACK)
 		return -EINVAL;
 
+	if (netif_is_ipvlan_port(dev))
+		return -EBUSY;
+
 	port = kzalloc(sizeof(*port), GFP_KERNEL);
 	if (port == NULL)
 		return -ENOMEM;