arm64: dts: rockchip: add DDC bus on Rock Pi 4

A DDC I2C bus specifier is required for DDC EDID probing to work
properly.

Fixes: 1b5715c6 ("arm64: dts: rockchip: add ROCK Pi 4 DTS support")
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-rock-pi-4.dts

@@ -158,6 +158,7 @@ &gmac {
 };
 
 &hdmi {
+	ddc-i2c-bus = <&i2c3>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&hdmi_cec>;
 	status = "okay";