arm64: dts: microchip: add LAN969x support

Add support for Microchip LAN969x switch SoC series by adding the SoC DTSI.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Acked-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://lore.kernel.org/r/20260302112153.464422-5-robert.marko@sartura.hr
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>

Author: robimarko