devkeys: switch container key from RSA to EC

Created by doing:
  openssl ecparam -name prime256v1 -out prime256v1.pem
  openssl ecparam -genkey -noout -out cros-oci-container.pem -in prime256v1.pem
  openssl pkey -in cros-oci-container.pem -out cros-oci-container-pub.pem -pubout

BUG=chromium:660209
TEST=`./sign_official_build.sh oci-container fastboot/ ../tests/devkeys` still works
BRANCH=None

Change-Id: I4171b2d9d9788cccf082d613b1de6e7ca9d0b005
Reviewed-on: https://chromium-review.googlesource.com/461418
Commit-Ready: Dylan Reid <dgreid@chromium.org>
Tested-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
2 files changed