arm64: allwinner: h5: Add initial Orangepi Zero Plus 2 support

Orangepi Zero Plus 2 is an open-source single-board computer
using the Allwinner h5 SOC.

H5 Orangepi Zero Plus 2 has
- Quad-core Cortex-A53
- 512MB DDR3
- micrSD slot and 8GB eMMC
- Debug TTL UART
- HDMI
- Wifi + BT
- OTG+power supply

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>