Add code for AmigaOne board
(preliminary merge to U-Boot, still WIP)

* Patch by Jon Diekema, 12 Nov 2002:
- Adding URL for IEEE OUI lookup
- Making the autoboot #defines dependent on CONFIG_AUTOBOOT_KEYED
being defined.
- In the CONFIG_EXTRA_ENV_SETTINGS #define, the root-on-initrd and
root-on-nfs macros are designed to switch how the default boot
method gets defined.