Fixup the migration compatibility for existing machine types
so that they do not enable msi-x.

Symptom:

(qemu) qemu: get_pci_config_device: Bad config data: i=0x34 read: 84 device: 98 cmask: ff wmask: 0 w1cmask:0
qemu: Failed to load PCIDevice:config
qemu: Failed to load virtio-rng:virtio
qemu: error while loading state for instance 0x0 of device '0000:00:03.0/virtio-rng'
qemu: load of migration failed: Invalid argument

Note: This fix will break migration from 7.2->7.2-fixed with this patch

bz: https://bugzilla.redhat.com/show_bug.cgi?id=2155749


Fixes: 9ea02e8f ("virtio-rng-pci: Allow setting nvectors, so we can use MSI-X")

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20230109105809.163975-1-dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: David Daney <david.daney@fungible.com>
Fixes: 9ea02e8f (&quot;virtio-rng-pci: Allow setting nvectors, so we can use MSI-X&quot;)<br>
Signed-off-by: Dr. David Alan Gilbert &amp;lt;&lt;a href="mailto:dgilbert@redhat.com" <target="_blank"&gt;dgilbert@redhat.com&lt;/a&gt;&amp;gt;&lt;br>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>