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>

drivers/video/omap2/dss/rfbi.c

@@ -1039,5 +1039,5 @@ int rfbi_init_platform_driver(void)
 
 void rfbi_uninit_platform_driver(void)
 {
-	return platform_driver_unregister(&omap_rfbihw_driver);
+	platform_driver_unregister(&omap_rfbihw_driver);
 }