EC sync: Add a new shared flag VB2_SD_STATUS_EC_SYNC_COMPLETE

The new flag can be set by any firmware which updates the EC to let
further stages know that the EC sync has already been completed during
this boot.

BUG=none
BRANCH=none
TEST=make runtests

Change-Id: Ide14efe7091631b62d240ddc984c8c70527a6d37
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1877066
Reviewed-by: Joel Kitching <kitching@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
2 files changed