The compat property was added by commit
9dbcca5a, and the pc-0.12 and older
machine-types were not changed because virtio-9p-pci was introduced on QEMU
0.13 (commit 9f107513). The only problem is
that this breaks the PC_COMPAT_* nesting pattern we currently use.

So, move the property to PC_COMPAT_0_13. This make pc-0.12 and older inherit
it, but that shouldn't be an issue as QEMU 0.12 didn't have virtio-9p-pci.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>