dt-bindings: hdmi-connector: add DDC I2C bus phandle documentation

Add an optional ddc-i2c-bus phandle property that points to
an I2C master controller that handles the connector DDC pins.
Signed-off-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Acked-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/connector/hdmi-connector.txt

@@ -8,6 +8,7 @@ Required properties:
 Optional properties:
 - label: a symbolic name for the connector
 - hpd-gpios: HPD GPIO number
+- ddc-i2c-bus: phandle link to the I2C controller used for DDC EDID probing
 
 Required nodes:
 - Video port for HDMI input