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>

drivers/video/omap2/dss/sdi.c

@@ -123,7 +123,7 @@ int omapdss_sdi_display_enable(struct omap_dss_device *dssdev)
 		goto err_sdi_enable;
 	mdelay(2);
 
-	dssdev->manager->enable(dssdev->manager);
+	dss_mgr_enable(dssdev->manager);
 
 	return 0;
 
@@ -145,7 +145,7 @@ EXPORT_SYMBOL(omapdss_sdi_display_enable);
 
 void omapdss_sdi_display_disable(struct omap_dss_device *dssdev)
 {
-	dssdev->manager->disable(dssdev->manager);
+	dss_mgr_disable(dssdev->manager);
 
 	dss_sdi_disable();