ARM: dts: add support for Laird WB50N cpu module and DVK

This adds support for Lairds CPU module, featuring Atheros wifi, CSR
Bluetooth and, Atmel SAMA5D3 CPU.
https://www.lairdtech.com/products/wb50nbt-wi-fi-bluetooth-module



Signed-off-by: Ben Whitten <ben.whitten@lairdtech.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>