[coreboot] [PATCH] Drop duplicate CBFS docs

[Uwe Hermann]

We currently have

- documentation/cbfs.txt
 - util/cbfstool/README (almost exact copy of the above)
 - http://www.coreboot.org/CBFS (wikified copy of the above).

Attached patch drops the two text files in favor for the wiki page,
which is a lot easier to keep up-to-date.

Uwe.