create_new_keys: add options for generating 4k keys

BUG=chromium:454651
TEST=`./create_new_keys.sh` still generates 8k keys
TEST=`./create_new_keys.sh --4k` now generates 4k keys
BRANCH=None

Change-Id: I2203536880b9320959fd741c4bbcf814aded603c
Reviewed-on: https://chromium-review.googlesource.com/245318
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
2 files changed