arc: Add missing keys to support signing ARC images.

This adds missing networkstack keys required for sign scripts.
Keys are generated by:
   ./create_new_android_keys.sh ${VBOOT_REFERENCE}/tests/devkeys/android
   git checkout media.pk8 media.x509.pem platform.pk8 \
                platform.x509.pem releasekey.pk8 releasekey.x509.pem \
                shared.pk8 shared.x509.pem

BUG=b:170344735
TEST=build hatch based board with this feature on
BRANCH=none

Change-Id: I80376b8b07cc111d3ef51cf8a7bbc8dcfe8cfcc8
Signed-off-by: Yury Khmel <khmel@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2803655
Reviewed-by: Victor Hsieh <victorhsieh@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed