arm64: dts: amlogic: a4: add ao secure node

arm64: dts: amlogic: a4: add ao secure node

Add node for board info registers, which allows getting SoC family and
board revision.

For example, with MESON_GX_SOCINFO config enabled we can get the
following information for board with Amlogic A4 SoC:
soc soc0: Amlogic A4 (A113L2) Revision 40:b (1:1) Detected.

Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240719-soc_info-v3-6-020a3b687c0c@amlogic.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>