OMAPDSS: hide manager's enable/disable()

omap_overlay_manager struct contains enable() and disable() functions.
However, these are only meant to be used from inside omapdss, and thus
it's bad to expose the functions.

This patch adds dss_mgr_enable() and dss_mgr_disable() functions to
apply.c, which handle enabling and disabling the output.

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 e6f961a..03c7244 100644
--- a/drivers/video/omap2/dss/dss.h
+++ b/drivers/video/omap2/dss/dss.h
@@ -169,6 +169,8 @@
 int dss_mgr_wait_for_go_ovl(struct omap_overlay *ovl);
 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);
+void dss_mgr_disable(struct omap_overlay_manager *mgr);
 
 /* display */
 int dss_suspend_all_devices(void);