arm64: dts: uniphier: add AVE ethernet node

Add nodes of the AVE ethernet controller for LD11 and LD20 SoCs
and the boards.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>