rockchip: Add initial support for the Pinebook Pro laptop from Pine64.

Specification:
- Rockchip RK3399
- 4GB Dual-Channel LPDDR4
- eMMC socket
- mSD card slot
- 128Mbit (16Mb) SPI Flash
- AP6256 for 11AC WiFi + BT5
- 14 inch 1920*1080 eDP MiPi display
- Camera
- USB 3.0, 2.0 ports
- Type-C port with alt-mode display (DP 1.2) and 15W charge
- DC 5V/3A
- optional PCIe slot for NVMe SSD drive

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Tested-by: Vagrant Cascadian <vagrant@debian.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>