OpenBIOS/xbox patch

[Rink Springer]

Hi everyone,

Based on Ed's work, I've made a patch to really make the XBox support
work :-) It contained two minor flaws, both of which are fixed by the
patch. If I apply it, I see the OpenBIOS welcome screen.

You can download it from
http://rink.nu/downloads/xbox-patches/openbios-xbox.diff. Feel free to
apply it in the tree.