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>

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

@@ -475,7 +475,7 @@ static int venc_power_on(struct omap_dss_device *dssdev)
 	if (r)
 		goto err1;
 
-	r = dss_mgr_enable(mgr);
+	r = dss_mgr_enable(mgr->id);
 	if (r)
 		goto err2;