ARM: dts: sun8i: Add initial Orangepi Zero Plus 2 H3 support

Orangepi Zero Plus 2 is an open-source single-board computer, available in two
Allwinner SOC variants, H3 and H5. We add support for H3 variant here, as the
H5 is already supported by sun50i-h5-orangepi-zero-plus2.dts.

H3 Orangepi Zero Plus 2 has:
- Quad-core Cortex-A7
- 512MB DDR3
- microSD slot and 8GB eMMC
- Debug TTL UART
- HDMI
- Wifi + BT
- OTG + power supply

Signed-off-by: Diego Rondini <diego.rondini@kynetics.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>