net: sparx5: add vlan support

This adds Sparx5 VLAN support.

Sparx5 has more VLAN features than provided here, but these will be added
in later series. For now we only add the basic L2 features.

Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: Bjarni Jonasson <bjarni.jonasson@microchip.com>
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>