arm64: dts: add board AN400

Add devicetrees support for Amlogic AN400  board based T7 SoC.

Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Link: https://lore.kernel.org/r/20230706091954.3301224-3-xianwei.zhao@amlogic.com


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>