rockchip: rk3399: Add ROC-RK3399-PC support

rockchip: rk3399: Add ROC-RK3399-PC support

Add initial support for ROC-RK3399-PC board.

Specification
- Rockchip RK3399
- LPDDR4 4GiB
- eMMC slot
- SD card slot
- RTL8211E 1Gbps
- HDMI Out, DP, MIPI DSI/CSI, EDP
- PCIe M.2
- USB 2.0, USB-3.0
- USB C Type

Commit details of rk3399-roc-pc.dts sync from Linux v5.2:
"arm64: dts: rockchip: add support for ROC-RK3399-PC board"
(sha1: 8bb878cf20ae10809c36db96993bfce7026d062b)

Signed-off-by: Levin Du <djw@t-chip.com.cn>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>