veth: Fix veth_dellink method

In commit 23289a37
(net: add a list_head parameter to dellink() method),
I forgot to actually use this parameter in veth_dellink.

I remember feeling a bit uncomfortable about veth_close(),
because it does :

netif_carrier_off(dev);
netif_carrier_off(priv->peer);

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>