drm/omap: convert dss_mgr_disable to accept omap_channel

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

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/output.c

@@ -222,9 +222,9 @@ int dss_mgr_enable(enum omap_channel channel)
 }
 EXPORT_SYMBOL(dss_mgr_enable);
 
-void dss_mgr_disable(struct omap_overlay_manager *mgr)
+void dss_mgr_disable(enum omap_channel channel)
 {
-	dss_mgr_ops->disable(mgr->id);
+	dss_mgr_ops->disable(channel);
 }
 EXPORT_SYMBOL(dss_mgr_disable);