Add nvramtool -C option that takes a CBFS file as argument.

Add nvramtool -C option that takes a CBFS file as argument.
When using this option, nvramtool looks for a cmos_layout.bin
and cmos.default in the image and uses these for layout information
and CMOS data.

Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Acked-by: Stefan Reinauer <stepan@coreboot.org>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6285 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1