rockchip: add support for Radxa Rock Pi 4

rockchip: add support for Radxa Rock Pi 4

This adds basic support for Radxa Rock Pi 4

Specification:
  - RAM:      1 GB/ 2 GB/4 GB LPDDR4

  - SoC:      Rockchip RK3399
  - CPU:      64bit hexa core processor
              Dual Cortex-A72, freqency 1.8Ghz
              with quad Cortex-A53, frequency 1.4Ghz
  - USB:      USB 3.0 OTG x1
              hardware switch for host/device switch, upper one
              USB 3.0 HOST x1
              dedicated USB3.0 channel, lower one
              USB 2.0 HOST x2
  - Ethernet: 1x GbE
  - Storage:  eMMC module
              uSD card
              M.2 SSD
  - Wireless: 802.11 ac wifi
              Bluetooth 5.0
              currently not supported

 firmware Installation
 ======================
 gzip -d xxx.img.gz, then dd the .img to SD/eMMC
 ======================

 Device Tested: ROCK PI 4 Model B v1.3

Signed-off-by: Marty Jones <mj8263788@gmail.com>