vboot/vboot_kernel: get kernel subkey from vb2_shared_data directly

This CL is part of a series to merge vboot1 and vboot2.0
kernel verification code; see b/181739551.

BUG=b:181739551
TEST=make clean && make runtests
BRANCH=none

Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: I155997d96d9edd2c6c2f8a731b8439a835156978
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2824766
Tested-by: Joel Kitching <kitching@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
2 files changed