arm64: dts: rockchip: enable cdn DP for rk3399 sapphire

As we had posted the DP firmeware to /lib/firmware/rockchip,
so you need check this path in your rootfs first, if enable the DP.

Change-Id: Id24a42edc9d6cd0b0de0a2dfefe2727df3965b67
Signed-off-by: Caesar Wang <wxt@rock-chips.com>

arch/arm64/boot/dts/rockchip/rk3399-sapphire.dtsi

@@ -192,6 +192,12 @@
 	};
 };
 
+&cdn_dp {
+	status = "okay";
+	extcon = <&fusb0>;
+	phys = <&tcphy0_dp>;
+};
+
 &cpu_l0 {
 	cpu-supply = <&vdd_cpu_l>;
 };