net: aquantia: implement vlan offload configuration

set_features should update flags and reinit hardware if
vlan offload settings were changed.

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