irqbypass: do not start cons/prod when failed connect

If failed to connect, there is no need to start consumer nor
producer.

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20200731065533.4144-7-lingshan.zhu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

virt/lib/irqbypass.c

@@ -40,17 +40,21 @@ static int __connect(struct irq_bypass_producer *prod,
 	if (prod->add_consumer)
 		ret = prod->add_consumer(prod, cons);
 
-	if (!ret) {
-		ret = cons->add_producer(cons, prod);
-		if (ret && prod->del_consumer)
-			prod->del_consumer(prod, cons);
-	}
+	if (ret)
+		goto err_add_consumer;
+
+	ret = cons->add_producer(cons, prod);
+	if (ret)
+		goto err_add_producer;
 
 	if (cons->start)
 		cons->start(cons);
 	if (prod->start)
 		prod->start(prod);
-
+err_add_producer:
+	if (prod->del_consumer)
+		prod->del_consumer(prod, cons);
+err_add_consumer:
 	return ret;
 }