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/venc.c b/drivers/video/omap2/dss/venc.c
index 9475e6e..1884e34 100644
--- a/drivers/video/omap2/dss/venc.c
+++ b/drivers/video/omap2/dss/venc.c
@@ -959,5 +959,5 @@
 	if (cpu_is_omap44xx())
 		return;
 
-	return platform_driver_unregister(&omap_venchw_driver);
+	platform_driver_unregister(&omap_venchw_driver);
 }