vboot: create 2kernel.c for kernel-related functions

Create 2kernel.c for kernel-related functions (including
both internal and API-facing).

Relocate functions which are currently in active use from
lib20/api_kernel.c to 2lib/2kernel.c.

Create vb2_kernel_tests.c and move appropriate tests there.
Tests for vb2_normal_boot (previously VbBootNormal) will
be added in a subsequent CL.

BUG=b:124141368, chromium:968464
TEST=make clean && make runtests
BRANCH=none

Change-Id: I153ea318ba238b7b30bf871105388437f63075d1
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2091126
Reviewed-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Tested-by: Joel Kitching <kitching@chromium.org>
10 files changed