arm64: dts: sparx5: Add the Sparx5 switch node

This provides the configuration for the currently available evaluation
boards PCB134 and PCB135.

The series depends on the following series currently on its way
into the kernel:

- Sparx5 Reset Driver
  Link: https://lore.kernel.org/r/20210416084054.2922327-1-steen.hegelund@microchip.com/



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