utility: Add "enable_dev_usb_boot".

A shortcut and easier way to enable USB booting without always calling the huge
firmware updater.

BRANCH=none
BUG=none
TEST=./enable_dev_usb_boot # successfully set dev_usb_boot value.

Change-Id: I9ebb3ce79ef58bc0a32926866d5e1827a92b6e74
Reviewed-on: https://gerrit.chromium.org/gerrit/33046
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
2 files changed