vboot/vboot_kernel: update keyblock flag mismatch logic

A keyblock flag mismatch should cause keyblock verification to
fail regardless of whether a valid keyblock is required (i.e.
self-signed keyblock case).

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

TEST=make clean && make runtests

Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: I47096ab7fcf0fbd47a46a9a92a5406e9aa9b3596
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2846251
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
2 files changed