netdev: restore MTU change operation

alloc_etherdev() used to install a default implementation of this
operation, but it must now be explicitly installed in struct
net_device_ops.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/arm/ixp4xx_eth.c

@@ -1142,6 +1142,7 @@ static const struct net_device_ops ixp4xx_netdev_ops = {
 	.ndo_start_xmit = eth_xmit,
 	.ndo_set_multicast_list = eth_set_mcast_list,
 	.ndo_do_ioctl = eth_ioctl,
+	.ndo_change_mtu = eth_change_mtu,
 	.ndo_set_mac_address = eth_mac_addr,
 	.ndo_validate_addr = eth_validate_addr,
 };