vboot/vboot_kernel: rewrite require_official_os

Function no longer needs the `params` argument.  Use more
precise language, replacing the term "OS" with "kernel".

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: Ie4162760744a6c341fee122c5be247d86bd49c05
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2741921
Tested-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
3 files changed