dt-bindings: display: add HPD gpio to DVI connector

Add hpd-gpios property to dvi-connector.txt.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

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

@@ -10,6 +10,7 @@ Optional properties:
 - analog: the connector has DVI analog pins
 - digital: the connector has DVI digital pins
 - dual-link: the connector has pins for DVI dual-link
+- hpd-gpios: HPD GPIO number
 
 Required nodes:
 - Video port for DVI input