bdb: Add vba_update_buc

vba_update_buc writes a BUC (boot unlock code) to NVM-RW. It will be called
by AP-RW to update a BUC.

BUG=chrome-os-partner:51907
BRANCH=tot
TEST=make runtests

Change-Id: Ic91f34b60b11ebce948bce01993ddb44519a59b8
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/346233
5 files changed