Add NV flag to default boot legacy OS

In developer mode, this option will make the system try to boot into
a legacy OS first after the 30 second timeout. This removes the need to
press a key during boot to try legacy mode and the need to remove the
write protect screw to boot legacy as default.

BUG=chromium:310697
BRANCH=none
TEST=make runtests

Change-Id: I9a9f64c14ad015e21d08eec36e8fc187189cd2f2
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/304077
Reviewed-by: Randall Spangler <rspangler@chromium.org>
17 files changed