PCI devices can't be plugged directly into PCI extra root bridges
because their resources can't be computed by firmware before the ACPI
tables are loaded.

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>