dt-bindings: arm: rockchip: Add Orange Pi R1 Plus

Add devicetree binding documentation for the Orange Pi R1 Plus.
Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221203074149.11543-2-amadeus@jmu.edu.cnSigned-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/arm/rockchip.yaml

@@ -778,6 +778,11 @@ properties:
           - const: tronsmart,orion-r68-meta
           - const: rockchip,rk3368
 
+      - description: Xunlong Orange Pi R1 Plus
+        items:
+          - const: xunlong,orangepi-r1-plus
+          - const: rockchip,rk3328
+
       - description: Zkmagic A95X Z2
         items:
           - const: zkmagic,a95x-z2