drm/omap: convert dss_mgr_enable to accept omap_channel

We are removing uses of 'struct omap_overlay_manager'. This patch
changes dss_mgr_enable() 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 f926ed7..cb90a9c 100644
--- a/drivers/gpu/drm/omapdrm/dss/output.c
+++ b/drivers/gpu/drm/omapdrm/dss/output.c
@@ -216,9 +216,9 @@
 }
 EXPORT_SYMBOL(dss_mgr_set_lcd_config);
 
-int dss_mgr_enable(struct omap_overlay_manager *mgr)
+int dss_mgr_enable(enum omap_channel channel)
 {
-	return dss_mgr_ops->enable(mgr->id);
+	return dss_mgr_ops->enable(channel);
 }
 EXPORT_SYMBOL(dss_mgr_enable);