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".
"
BUG=chromium:812290
TEST=None
Change-Id: I6c8a9945d67e37ab6bb8b540be0a3404c75e4f34
Reviewed-on: https://chromium-review.googlesource.com/c/1461163
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Commit-Queue: Bernie Thompson <bhthompson@chromium.org>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
