[Soekris] Need to downgrade firmware on net4801

[Stuart Henderson]

>> Can somebody PLEASE tell me how to downgrade my firmware back to 1.28,
>
> Download 1.28 as normal then use 'upgrade -f' to force it to accept the
> downgrade.

Note the warning on the BIOS download page:

:: It is not recommended to "downgrade" a BIOS to an older version
:: than the one a board is supplied with.

I imagine this is particularly pertinent with very recent boards;
from the release notes:

  * added support for new BIOS flash chip for net48xx

Presumably the flash chip has changed and isn't supported by
old BIOS versions.