resign_firmwarefd.sh: support new "flag" (for hinting two-stop FW)

The two-stop firmware relies on the "flag" field which may be useful for the
resign_firmwarefd.sh.

BUG=chrome-os-partner:5095
TEST=./resign_firmwarefd [params] 1
     vbutil_firmware --verify ..... # seeing flag = 1

Change-Id: I56b44ee5b610e36384e15e6eb31286f0f838734b
Reviewed-on: http://gerrit.chromium.org/gerrit/4561
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Gaurav Shah <gauravsh@chromium.org>
2 files changed