filter-graph: emit control change after loading

Always do a control change to the instances when they are created. This
is to make sure the internal state is synced to the control values.

The sofa filter and biquads need this to correctly configure themselves
after a suspend.

Fixes #5152

spa/plugins/filter-graph/filter-graph.c

@@ -1645,6 +1645,7 @@ static int impl_activate(void *object, const struct spa_dict *props)
 				goto error;
 			}
 		}
+		node->control_changed = true;
 	}
 
 	/* then link ports */