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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/macvlan.c

···
 	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;