vboot: update vboot2 functions to use new vb2_error_t

To make explicit when vboot2 error codes should be returned,
use the new vb2_error_t type on all functions which return
VB2_ERROR_* constants.

BUG=b:124141368, chromium:988410
TEST=make clean && make runtests

Change-Id: Idd3ee8afe8c78347783ce5fa829cb78f1e5719e2
Signed-off-by: Joel Kitching <kitching@google.com>
Cq-Depend: chromium:1728113, chromium:1728499
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1728292
Reviewed-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Tested-by: Joel Kitching <kitching@chromium.org>
84 files changed