OMAP: DSS2: move set/get_mirror()

Move set/get_mirror() 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 3f345b8..8b91796 100644
--- a/drivers/video/omap2/dss/display.c
+++ b/drivers/video/omap2/dss/display.c
@@ -215,9 +215,9 @@
 {
 	struct omap_dss_device *dssdev = to_dss_device(dev);
 	int mirror;
-	if (!dssdev->get_mirror)
+	if (!dssdev->driver->get_mirror)
 		return -ENOENT;
-	mirror = dssdev->get_mirror(dssdev);
+	mirror = dssdev->driver->get_mirror(dssdev);
 	return snprintf(buf, PAGE_SIZE, "%u\n", mirror);
 }
 
@@ -228,12 +228,12 @@
 	unsigned long mirror;
 	int r;
 
-	if (!dssdev->set_mirror || !dssdev->get_mirror)
+	if (!dssdev->driver->set_mirror || !dssdev->driver->get_mirror)
 		return -ENOENT;
 
 	mirror = simple_strtoul(buf, NULL, 0);
 
-	r = dssdev->set_mirror(dssdev, mirror);
+	r = dssdev->driver->set_mirror(dssdev, mirror);
 	if (r)
 		return r;