OMAP: DSS2: move get_resolution()

Move get_resolution() 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/dsi.c b/drivers/video/omap2/dss/dsi.c
index b478a50..abc66f2 100644
--- a/drivers/video/omap2/dss/dsi.c
+++ b/drivers/video/omap2/dss/dsi.c
@@ -2868,7 +2868,7 @@
 
 			DSSDBG("starting auto update\n");
 
-			dssdev->get_resolution(dssdev, &w, &h);
+			dssdev->driver->get_resolution(dssdev, &w, &h);
 
 			dsi_set_update_region(dssdev, 0, 0, w, h);
 
@@ -3422,7 +3422,7 @@
 	if (dssdev->state != OMAP_DSS_DISPLAY_ACTIVE)
 		goto end;
 
-	dssdev->get_resolution(dssdev, &dw, &dh);
+	dssdev->driver->get_resolution(dssdev, &dw, &dh);
 
 	if  (x > dw || y > dh)
 		goto end;