arm64: dts: allwinner: orange-pi-3: Enable HDMI output

Orange Pi 3 has a DDC_CEC_EN signal connected to PH2, that enables the DDC
I2C bus voltage shifter. Before EDID can be read, we need to pull PH2 high.
This is realized by the ddc-en-gpios property.

Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>