OMAP: DSS2: move set/get_update_mode()

Move set/get_update_mode() from omap_dss_device to omap_dss_driver.

This is part of a larger patch-set, which moves the control from omapdss
driver to the display driver.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>
diff --git a/drivers/video/omap2/dss/display.c b/drivers/video/omap2/dss/display.c
index 383a8c8..86996d8 100644
--- a/drivers/video/omap2/dss/display.c
+++ b/drivers/video/omap2/dss/display.c
@@ -69,8 +69,8 @@
 {
 	struct omap_dss_device *dssdev = to_dss_device(dev);
 	enum omap_dss_update_mode mode = OMAP_DSS_UPDATE_AUTO;
-	if (dssdev->get_update_mode)
-		mode = dssdev->get_update_mode(dssdev);
+	if (dssdev->driver->get_update_mode)
+		mode = dssdev->driver->get_update_mode(dssdev);
 	return snprintf(buf, PAGE_SIZE, "%d\n", mode);
 }
 
@@ -94,7 +94,7 @@
 		return -EINVAL;
 	}
 
-	r = dssdev->set_update_mode(dssdev, mode);
+	r = dssdev->driver->set_update_mode(dssdev, mode);
 	if (r)
 		return r;