dt-bindings: net: renesas,etheravb: Add r8a779a0 support

Document the compatible value for the RAVB block in the Renesas R-Car
V3U (R8A779A0) SoC. This variant has no stream buffer, so we only need
to add the new compatible and add it to the TX delay block.
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210121100619.5653-2-wsa+renesas@sang-engineering.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/renesas,etheravb.yaml

@@ -40,6 +40,7 @@ properties:
               - renesas,etheravb-r8a77980     # R-Car V3H
               - renesas,etheravb-r8a77990     # R-Car E3
               - renesas,etheravb-r8a77995     # R-Car D3
+              - renesas,etheravb-r8a779a0     # R-Car V3U
           - const: renesas,etheravb-rcar-gen3 # R-Car Gen3 and RZ/G2
 
   reg: true
@@ -170,6 +171,7 @@ allOf:
               - renesas,etheravb-r8a77965
               - renesas,etheravb-r8a77970
               - renesas,etheravb-r8a77980
+              - renesas,etheravb-r8a779a0
     then:
       required:
         - tx-internal-delay-ps