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>
diff --git a/drivers/net/fec.c b/drivers/net/fec.c
index 0f19b74..d4b9807 100644
--- a/drivers/net/fec.c
+++ b/drivers/net/fec.c
@@ -1642,6 +1642,7 @@
 	.ndo_stop		= fec_enet_close,
 	.ndo_start_xmit		= fec_enet_start_xmit,
 	.ndo_set_multicast_list = set_multicast_list,
+	.ndo_change_mtu		= eth_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_tx_timeout		= fec_timeout,
 	.ndo_set_mac_address	= fec_set_mac_address,