hw/virtio: fix double use of a virtio flag

Commits 1811e64 and a6df8ad use the same virtio feature bit 4
for different features.

Fix it by using different bits.

Reported-by: Laurent Vivier <lvivier@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 631a438)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

hw/virtio/virtio-pci.h

@@ -72,7 +72,7 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
 /* virtio version flags */
 #define VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT 2
 #define VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT 3
-#define VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT 4
+#define VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT 6
 #define VIRTIO_PCI_FLAG_DISABLE_LEGACY (1 << VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT)
 #define VIRTIO_PCI_FLAG_DISABLE_MODERN (1 << VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT)
 #define VIRTIO_PCI_FLAG_DISABLE_PCIE (1 << VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT)