arm64: dts: renesas: r8a774b1: Add Ethernet AVB node

This patch adds the SoC specific part of the Ethernet AVB
device tree node.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1569831527-1250-5-git-send-email-biju.das@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>