Replace coreboot contents with README.txt file

As Chrome OS does not use the master branch of coreboot, we stub
it out with just a README.txt file.

These are not the sources you are looking for.

The master branch of Coreboot is not used for Chrome OS.

Please pick a chromeos-* branch, most likely "chromeos-2016.05".


Change-Id: I6c8a9945d67e37ab6bb8b540be0a3404c75e4f34
Reviewed-by: Bernie Thompson <>
Commit-Queue: Bernie Thompson <>
Tested-by: Bernie Thompson <>