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.cn


Signed-off-by: Heiko Stuebner <heiko@sntech.de>