hw/pci-bridge: Add missing unref in case register-bus fails

The error paths after a successful qdev_create/pci_bus_new
should contain a object_unref/object_unparent.
pxb_dev_init_common() did not yet, so add it.

Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>

hw/pci-bridge/pci_expander_bridge.c

@@ -249,7 +249,7 @@ static int pxb_dev_init_common(PCIDevice *dev, bool pcie)
     PCI_HOST_BRIDGE(ds)->bus = bus;
 
     if (pxb_register_bus(dev, bus)) {
-        return -EINVAL;
+        goto err_register_bus;
     }
 
     qdev_init_nofail(ds);
@@ -263,6 +263,12 @@ static int pxb_dev_init_common(PCIDevice *dev, bool pcie)
 
     pxb_dev_list = g_list_insert_sorted(pxb_dev_list, pxb, pxb_compare);
     return 0;
+
+err_register_bus:
+    object_unref(OBJECT(bds));
+    object_unparent(OBJECT(bus));
+    object_unref(OBJECT(ds));
+    return -EINVAL;
 }
 
 static int pxb_dev_initfn(PCIDevice *dev)