virtio-pci: return error if virtio_console_init fails

Currently only one virtio_console device is supported. Trying to add
multiple devices fails and such failure should be reported back to the
qdev init functions.
Signed-off-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/virtio-pci.c

@@ -473,6 +473,9 @@ static int virtio_console_init_pci(PCIDevice *pci_dev)
         proxy->class_code = PCI_CLASS_COMMUNICATION_OTHER;
 
     vdev = virtio_console_init(&pci_dev->qdev);
+    if (!vdev) {
+        return -1;
+    }
     virtio_init_pci(proxy, vdev,
                     PCI_VENDOR_ID_REDHAT_QUMRANET,
                     PCI_DEVICE_ID_VIRTIO_CONSOLE,