[coreboot] three errors found while compiling FILO (1 fix + 1 workaround)

[Andrew Engelbrecht]

Patrick Georgi wrote:
> These are with filo 0.6.0, right? It depends on an age-old version of 
> libpayload. We had a build blocker there, so I couldn't create a new 
> FILO version.

those issues applied to both versions 0.6.0 and master, except for the
one which involving checking out the master branch.