dt-bindings: pwm: rockchip: Add description for rk3588

Add "rockchip,rk3588-pwm" compatible string for PWM nodes found
on a rk3588 platform.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-rockchip.yaml

@@ -30,6 +30,7 @@ properties:
               - rockchip,px30-pwm
               - rockchip,rk3308-pwm
               - rockchip,rk3568-pwm
+              - rockchip,rk3588-pwm
           - const: rockchip,rk3328-pwm
 
   reg: