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

Documentation/devicetree/bindings/arm/sunxi.yaml

@@ -1013,6 +1013,11 @@ properties:
           - const: xunlong,orangepi-zero2
           - const: allwinner,sun50i-h616
 
+      - description: Xunlong OrangePi Zero 2W
+        items:
+          - const: xunlong,orangepi-zero2w
+          - const: allwinner,sun50i-h618
+
       - description: Xunlong OrangePi Zero 3
         items:
           - const: xunlong,orangepi-zero3