Don't leak VLANClientState on PCI hot remove

destroy_nic() requires that NICInfo::private by a PCIDevice pointer,
but then goes on to require that the same pointer matches
VLANClientState::opaque.

That is no longer the case for virtio-net since qdev and wasn't
previously the case for rtl8139, ne2k_pci or eepro100.

Make the situation a lot more clear by maintaining a VLANClientState
pointer in NICInfo.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/qdev.c b/hw/qdev.c
index 4c55009..83e98bf 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -250,8 +250,9 @@
 {
     NICInfo *nd = dev->nd;
     assert(nd);
-    return qemu_new_vlan_client(nd->vlan, nd->model, nd->name, can_receive,
-                                receive, receive_iov, cleanup, opaque);
+    nd->vc = qemu_new_vlan_client(nd->vlan, nd->model, nd->name, can_receive,
+                                  receive, receive_iov, cleanup, opaque);
+    return nd->vc;
 }