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

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: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210121100619.5653-2-wsa+renesas@sang-engineering.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>