sunxi: h3: Add initial ZeroPi support

ZeroPi is a new board of high performance with low cost
designed by FriendlyElec., using the Allwinner H3 SOC.

ZeroPi features
- Allwinner H3, Quad-core Cortex-A7@1.2GHz
- 256MB/512MB DDR3 RAM
- microsd slot
- 10/100/1000Mbps Ethernet
- Debug Serial Port
- DC 5V/2A power-supply

Signed-off-by: Yu-Tung Chang <mtwget@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>