ipip, sit: fix ipv4_{update_pmtu,redirect} calls

ipv4_{update_pmtu,redirect} were called with tunnel's ifindex (t->dev is a
tunnel netdevice). It caused wrong route lookup and failure of pmtu update or
redirect. We should use the same ifindex that we use in ip_route_output_* in
*tunnel_xmit code. It is t->parms.link .

Signed-off-by: Dmitry Popov <ixaphire@qrator.net>
Signed-off-by: David S. Miller <davem@davemloft.net>