vboot2: More specific errors for unimplemented external APIs

When porting vboot2 to a platform, it's common to copy 2stub.c and
then start implementing APIs.  Adding explicit errors makes it clearer
when an unimplemented API is called.

BUG=chromium:370082
BRANCH=none
TEST=VBOOT2=1 make runtests

Change-Id: I1f412b7ed4b431dbdbdee5e33b27bf7206186918
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/204960
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
2 files changed