Separate virtio PCI code

Split the PCI host bindings from the VRing transport implementation.

Signed-off-by: Paul Brook <paul@codesourcery.com>
diff --git a/hw/pci.c b/hw/pci.c
index 644e8f7..bdf3941 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -806,7 +806,7 @@
     "rtl8139",
     "e1000",
     "pcnet",
-    "virtio_net",
+    "virtio-net-pci",
     NULL
 };