arm64: dts: amlogic: add support for Radxa Zero

Radxa Zero is a small form factor SBC based on the Amlogic S905Y2
chipset that ships in a number of RAM/eMMC configurations:

Boards with 512MB/1GB LPDDR4 RAM have no eMMC storage and BCM43436
wireless (2.4GHz b/g/n) while 2GB/4GB boards have 8/16/32/64/128GB
eMMC storage and BCM4345 wireless (2.4/5GHz a/b/g/n/ac).

- Amlogic S905Y2 quad-core Cortex-A53
- Mali G31-MP2 GPU
- HDMI 2.1 output (micro)
- 1x USB 2.0 port - Type C (OTG)
- 1x USB 3.0 port - Type C (Host)
- 1x micro SD Card slot
- 40 Pin GPIO header

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20210909102154.22710-3-christianshewitt@gmail.com