vboot2: add support for verify data / digest using new signature struct

This adds the vb2_signature2 equivalents of vb2_verify_digest() and
vb2_verify_data(), including support for bare hash signatures.

BUG=chromium:423882
BRANCH=none
TEST=VBOOT2=1 make runtests

Change-Id: I372c9e5f0be926a833e4ca8f84665cfb05907481
Reviewed-on: https://chromium-review.googlesource.com/226950
Tested-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Queue: Randall Spangler <rspangler@chromium.org>
6 files changed