spec says we must, so let's do it!

Note: the implementation is incorrect for BE targets.
Will fix with a patch on top, not a big deal now as
the only user is seabios, used on x86 only.
Tested-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>