arm: dts: rockchip: add Radxa ROCK 4C+

Linux commit 246450344dad arm64: dts: rockchip: rk3399: Radxa ROCK 4C+

Add support for Radxa ROCK 4C+ SBC.

Key differences of 4C+ compared to previous ROCK Pi 4.
- Rockchip RK3399-T SoC
- DP from 4C replaced with micro HDMI 2K@60fps
- 4-lane MIPI DSI with 1920*1080
- RK817 Audio codec

Also, an official naming convention from Radxa mention to remove
Pi from board name, so this 4C+ is named as Radxa ROCK 4C+ not
Radxa ROCK Pi 4C+.

Signed-off-by: Stephen Chen <stephen@radxa.com>
Signed-off-by: Manoj Sai <abbaraju.manojsai@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: FUKAUMI Naoki <naoki@radxa.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>