OMAPDSS: remove return from platform_driver_unreg

For unknown reasons we seem to have a return in each of the omapdss's
uninit functions, which is a void function.

Remove the returns.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/dss.c b/drivers/video/omap2/dss/dss.c
index e212acb..3a06550 100644
--- a/drivers/video/omap2/dss/dss.c
+++ b/drivers/video/omap2/dss/dss.c
@@ -874,5 +874,5 @@
 
 void dss_uninit_platform_driver(void)
 {
-	return platform_driver_unregister(&omap_dsshw_driver);
+	platform_driver_unregister(&omap_dsshw_driver);
 }