arm64: dts: rockchip: add ROCK Pi 4 DTS support

arm64: dts: rockchip: add ROCK Pi 4 DTS support

ROCK Pi 4 is RK3399 based SBC from radxa.com. board has a 1G/2G/4G lpddr4, CSI,
DSI, HDMI, OTG, USB 2.0, USB 3.0, 10/100/1000 RGMII Ethernet Phy, es8316 codec,
POE, WIFI (for Model B only), PCIE M.2 support on board.

This patch enables
- HDMI Display
- Console
- MMC, EMMC
- USB 2.0, USB-3.0
- Ethernet

Signed-off-by: Akash Gajjar <Akash_Gajjar@mentor.com>
Signed-off-by: Pragnesh Patel <Pragnesh_Patel@mentor.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>