net: fix psock_fanout on sparc64

The packetsocket fanout test uses a packet ring. Use TPACKET_V2
instead of TPACKET_V1 to work around a known 32/64 bit issue in
the older ring that manifests on sparc64.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>