grunt: Add src/board dir

Based on Kahlee.
- Remove Audio, AHCI, and TPM.
- Add TODOs to add correct audio solution and add TPM.

BUG=b:64932381
TEST=emerge-grunt chromeos-bootimage
BRANCH=None

Change-Id: Iaf983249c66887a369724428ff219b5fbbb5904b
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://chromium-review.googlesource.com/777893
Commit-Ready: Martin Roth <martinroth@chromium.org>
Tested-by: Martin Roth <martinroth@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Chris Ching <chingcodes@chromium.org>
3 files changed