net: aquantia: added vlan offload related macros and functions

Register declaration macros required to work with vlan offload mode.

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>