net: atlantic: enable ipv6 support for TCP LSO and UDP GSO

This patch enables ipv6 support for TCP LSO and UDP GSO.
The code itself (aq_nic_map_skb) was ready for this after udp gso feature,
but corresponding NETIF_F_TSO6 wasn't enabled.

We now have tested both tcp and udp v6 GSO, and enabling them safely.

Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>