The vdev field is complicated to synchronize. Just access the
BusState's list of children.
Cc: qemu-stable@nongnu.org
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Andreas Faerber <afaerber@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>