dt-bindings: i2c: i2c-rk3x: add rk3588 compatible

Just like RK356x, RK3588 is compatible to the existing rk3399 binding.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/i2c/i2c-rk3x.yaml

@@ -37,6 +37,7 @@ properties:
               - rockchip,rk3308-i2c
               - rockchip,rk3328-i2c
               - rockchip,rk3568-i2c
+              - rockchip,rk3588-i2c
           - const: rockchip,rk3399-i2c
 
   reg: