dt-bindings: net: rockchip-dwmac: add rv1126 compatible

Add compatible string for RV1126 gmac, and constrain it to
be compatible with Synopsys dwmac 4.20a.
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Jagan Teki <jagan@edgeble.ai>
Signed-off-by: Anand Moon <anand@edgeble.ai>
Link: https://lore.kernel.org/r/20220920140944.2535-1-anand@edgeble.aiSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/rockchip-dwmac.yaml

@@ -27,6 +27,7 @@ select:
           - rockchip,rk3568-gmac
           - rockchip,rk3588-gmac
           - rockchip,rv1108-gmac
+          - rockchip,rv1126-gmac
   required:
     - compatible
 
@@ -48,6 +49,7 @@ properties:
               - rockchip,rk3368-gmac
               - rockchip,rk3399-gmac
               - rockchip,rv1108-gmac
+              - rockchip,rv1126-gmac
       - items:
           - enum:
               - rockchip,rk3568-gmac