dm: video: Add support for video bridges

A video bridge typically converts video from one format to another, e.g.
DisplayPort to LVDS. Add driver model support for these with a simple
interface to control activation and backlight. The uclass supports GPIO
control of power and reset lines.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 777b101..c744044 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -57,6 +57,7 @@
 	UCLASS_USB,		/* USB bus */
 	UCLASS_USB_DEV_GENERIC,	/* USB generic device */
 	UCLASS_USB_HUB,		/* USB hub */
+	UCLASS_VIDEO_BRIDGE,	/* Video bridge, e.g. DisplayPort to LVDS */
 
 	UCLASS_COUNT,
 	UCLASS_INVALID = -1,