dt-bindings: display: rockchip,dw-mipi-dsi: Document RK3128 DSI

Document the MIPI DSI controller for Rockchip RK3128. The integration is
similar to PX30 so it's bindings-constraints can be re-used.
Signed-off-by: Alex Bee <knaerzche@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240509140653.168591-2-knaerzche@gmail.com

Documentation/devicetree/bindings/display/rockchip/rockchip,dw-mipi-dsi.yaml

@@ -15,6 +15,7 @@ properties:
     items:
       - enum:
           - rockchip,px30-mipi-dsi
+          - rockchip,rk3128-mipi-dsi
           - rockchip,rk3288-mipi-dsi
           - rockchip,rk3399-mipi-dsi
           - rockchip,rk3568-mipi-dsi
@@ -77,6 +78,7 @@ allOf:
           contains:
             enum:
               - rockchip,px30-mipi-dsi
+              - rockchip,rk3128-mipi-dsi
               - rockchip,rk3568-mipi-dsi
               - rockchip,rv1126-mipi-dsi