dt-bindings: display: rockchip-vop: Document rv1126 vop

The VOP on Rockchip's RV1126 SoC is different from other SoC's
VOP implementations, so add a separate compatible for it.

Signed-off-by: Jagan Teki <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/display/rockchip/rockchip-vop.yaml

···
       - rockchip,rk3368-vop
       - rockchip,rk3399-vop-big
       - rockchip,rk3399-vop-lit
+      - rockchip,rv1126-vop
 
   reg:
     minItems: 1