dt-bindings: arm: sunxi: add Orange Pi Zero 2W

The Orange Pi Zero 2W is a small board with an Allwinner H618 SoC.

Add the compatible string to the binding documents.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231020145706.705420-2-andre.przywara@arm.com


Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>