dt-bindings: display: rockchip: Add rk3576 to RK3588 DW DSI2 controller schema

The rk3576 controller is based on the same newer Synopsis IP as the one
found in the rk3588.

Its external setting bits in the GRF are different though, so it needs
its own distinct compatible.

Acked-by: "Rob Herring (Arm)" <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

Documentation/devicetree/bindings/display/rockchip/rockchip,rk3588-mipi-dsi2.yaml

···
 properties:
   compatible:
     enum:
+      - rockchip,rk3576-mipi-dsi2
       - rockchip,rk3588-mipi-dsi2
 
   reg: