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/dsi.c b/drivers/video/omap2/dss/dsi.c
index d18c8e2..43eeb0d 100644
--- a/drivers/video/omap2/dss/dsi.c
+++ b/drivers/video/omap2/dss/dsi.c
@@ -4814,5 +4814,5 @@
 
 void dsi_uninit_platform_driver(void)
 {
-	return platform_driver_unregister(&omap_dsihw_driver);
+	platform_driver_unregister(&omap_dsihw_driver);
 }