OMAPDSS: APPLY: add return value to dss_mgr_enable()

Now that dss_mgr_enable() can fail due to checks, make it return the
error value.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/video/omap2/dss/dss.h b/drivers/video/omap2/dss/dss.h
index 6fce310..45b724a 100644
--- a/drivers/video/omap2/dss/dss.h
+++ b/drivers/video/omap2/dss/dss.h
@@ -170,7 +170,7 @@
 void dss_mgr_start_update(struct omap_overlay_manager *mgr);
 int omap_dss_mgr_apply(struct omap_overlay_manager *mgr);
 
-void dss_mgr_enable(struct omap_overlay_manager *mgr);
+int dss_mgr_enable(struct omap_overlay_manager *mgr);
 void dss_mgr_disable(struct omap_overlay_manager *mgr);
 int dss_mgr_set_info(struct omap_overlay_manager *mgr,
 		struct omap_overlay_manager_info *info);