Add the coreboot config to CBFS

Add the coreboot config to CBFS

The CBFS will contain a new file, named 'config' of type 'raw' that is a
stripped-down version of the .config file that was used to build the
current coreboot image. For space savings, all the comments and empty
lines were removed from the original config, except for one that lists
the coreboot git revision that's built into the image.

This is done in order to easily reproduce the work of  someone else when
only having their ROM image. In theory the reproduce could even be
automated by a new dedicated make target.

This should work even with abuild now.

Change-Id: I784989aac0227d3679d30314b06dadaec402749e
Signed-off-by: Cristian Măgherușan-Stanciu <cristi.magherusan@gmail.com>
Reviewed-on: http://review.coreboot.org/46
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>