drm/omap: convert dss_mgr_start_update to accept omap_channel

We are removing uses of 'struct omap_overlay_manager'. This patch
changes dss_mgr_start_update() to accept 'enum omap_channel' instead of
'struct omap_overlay_manager'.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
diff --git a/drivers/gpu/drm/omapdrm/dss/output.c b/drivers/gpu/drm/omapdrm/dss/output.c
index c623874..39a0d7f 100644
--- a/drivers/gpu/drm/omapdrm/dss/output.c
+++ b/drivers/gpu/drm/omapdrm/dss/output.c
@@ -228,9 +228,9 @@
 }
 EXPORT_SYMBOL(dss_mgr_disable);
 
-void dss_mgr_start_update(struct omap_overlay_manager *mgr)
+void dss_mgr_start_update(enum omap_channel channel)
 {
-	dss_mgr_ops->start_update(mgr->id);
+	dss_mgr_ops->start_update(channel);
 }
 EXPORT_SYMBOL(dss_mgr_start_update);