arm64: dts: add support for S4 based Amlogic AQ222

Add basic support for the Amlogic S4 based Amlogic AQ222 board:
which describe components as follows: CPU, GIC, IRQ, Timer, UART.
It's capable of booting up into the serial console.

Signed-off-by: Xianwei Zhao <xianwei.zhao@amlogic.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
[narmstrong: fixed memory unit address warning]
Link: https://lore.kernel.org/r/20220106112214.6987-1-xianwei.zhao@amlogic.com