virtio-serial: Cleanup on device hot-unplug

Free malloc'ed memory, unregister from savevm and clean up virtio-common
bits on device hot-unplug.

This was found performing a migration after device hot-unplug.

Reported-by: <lihuang@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 17c3d15..82a6d78 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -599,6 +599,14 @@
     return 0;
 }
 
+static int virtio_serial_exit_pci(PCIDevice *pci_dev)
+{
+    VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
+
+    virtio_serial_exit(proxy->vdev);
+    return virtio_exit_pci(pci_dev);
+}
+
 static int virtio_net_init_pci(PCIDevice *pci_dev)
 {
     VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
@@ -689,7 +697,7 @@
         .qdev.alias = "virtio-serial",
         .qdev.size = sizeof(VirtIOPCIProxy),
         .init      = virtio_serial_init_pci,
-        .exit      = virtio_exit_pci,
+        .exit      = virtio_serial_exit_pci,
         .qdev.props = (Property[]) {
             DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
                                DEV_NVECTORS_UNSPECIFIED),