net:ethernet:aquantia: Fix packet type detection (TCP/UDP) for IPv6.

In order for the checksum offloads to work correctly we need to set the
packet type bit (TCP/UDP) in the TX context buffer.

Fixes: 97bde5c4 ("net: ethernet: aquantia: Support for NIC-specific code")

Signed-off-by: Pavel Belous <pavel.belous@aquantia.com>
Tested-by: David Arcari <darcari@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>