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/venc.c b/drivers/video/omap2/dss/venc.c
index 7533458..101fcd7 100644
--- a/drivers/video/omap2/dss/venc.c
+++ b/drivers/video/omap2/dss/venc.c
@@ -447,7 +447,7 @@
 	if (dssdev->platform_enable)
 		dssdev->platform_enable(dssdev);
 
-	dssdev->manager->enable(dssdev->manager);
+	dss_mgr_enable(dssdev->manager);
 }
 
 static void venc_power_off(struct omap_dss_device *dssdev)
@@ -455,7 +455,7 @@
 	venc_write_reg(VENC_OUTPUT_CONTROL, 0);
 	dss_set_dac_pwrdn_bgz(0);
 
-	dssdev->manager->disable(dssdev->manager);
+	dss_mgr_disable(dssdev->manager);
 
 	if (dssdev->platform_disable)
 		dssdev->platform_disable(dssdev);