drm/omap: convert dss_mgr_set_timings to accept omap_channel

We are removing uses of 'struct omap_overlay_manager'. This patch
changes dss_mgr_set_timings() 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/dpi.c

@@ -359,7 +359,7 @@ static int dpi_set_mode(struct dpi_data *dpi)
 		t->pixelclock = pck;
 	}
 
-	dss_mgr_set_timings(mgr, t);
+	dss_mgr_set_timings(mgr->id, t);
 
 	return 0;
 }