net: sparx5: add switching support

This adds SwitchDev support by hardware offloading the
software bridge.

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>