net: sparx5: add the basic sparx5 driver

This adds the Sparx5 basic SwitchDev driver framework with IO range
mapping, switch device detection and core clock configuration.

Support for ports, phylink, netdev, mactable etc. are in the following
patches.

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>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>