gma500/cdv: Add eDP support

Introduce the eDP support into the driver.

This has been reworked a bit because kernel driver proper uses encoder/connectors
while the legacy Intel driver uses the old output stuff.

It also diverges on the backlight handling. The legacy Intel driver adds a panel
abstraction based upon the i915 one. It's only really used for backlight bits
and we have a perfectly good backlight abstraction which can extend instead.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
[ported to upstream driver, redid backlight abstraction]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/gma500/mdfld_dsi_output.c b/drivers/gpu/drm/gma500/mdfld_dsi_output.c
index 5675d93..32dba2a 100644
--- a/drivers/gpu/drm/gma500/mdfld_dsi_output.c
+++ b/drivers/gpu/drm/gma500/mdfld_dsi_output.c
@@ -299,17 +299,8 @@
 		if (drm_connector_property_set_value(connector, property,
 									value))
 			goto set_prop_error;
-		else {
-#ifdef CONFIG_BACKLIGHT_CLASS_DEVICE
-			struct backlight_device *psb_bd;
-
-			psb_bd = mdfld_get_backlight_device();
-			if (psb_bd) {
-				psb_bd->props.brightness = value;
-				mdfld_set_brightness(psb_bd);
-			}
-#endif
-		}
+		else
+			gma_backlight_set(encoder->dev, value);
 	}
 set_prop_done:
 	return 0;