dt-bindings: serial: snps-dw-apb-uart: Add Rockchip RK3588

Add a Rockchip RK3588 compatible.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20220623161350.242079-1-sebastian.reichel@collabora.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml

@@ -33,6 +33,7 @@ properties:
               - rockchip,rk3368-uart
               - rockchip,rk3399-uart
               - rockchip,rk3568-uart
+              - rockchip,rk3588-uart
               - rockchip,rv1108-uart
           - const: snps,dw-apb-uart
       - items: