arm64: dts: rockchip: add support for firefly-rk3399 board

Firefly-rk3399 is a bord from T-Firefly, you can find detail about
it here:
http://en.t-firefly.com/en/firenow/Firefly_RK3399/

This patch add basic node for the board and make it able to bring
up.

Peripheral works:
- usb hub which connect to ehci controller;
- UART2 debug
- eMMC
- PCIe

Not work:
- USB 3.0 HOST, type-C port
- sdio, sd-card

Not test for other peripheral:
- HDMI
- Ethernet
- OPTICAL
- WiFi/BT
- MIPI CSI/DSI
- IR
- EDP/DP
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/Makefile

@@ -5,6 +5,7 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3368-orion-r68-meta.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3368-px5-evb.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3368-r88.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-evb.dtb
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-firefly.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3399-gru-kevin.dtb
 
 always		:= $(dtb-y)