net: aquantia: vlan offloads logic in datapath

Update datapath by adding logic related to hardware assisted
vlan strip/insert behaviour.

Tested-by: Nikita Danilov <ndanilov@aquantia.com>
Signed-off-by: Igor Russkikh <igor.russkikh@aquantia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>