vboot2: Use more specific error codes, part 3

Error codes reported by 2common.c are now very specific, and tests
verify the proper errors are reported.

BUG=chromium:370082
BRANCH=none
TEST=make clean && VBOOT2=1 COV=1 make

Change-Id: I9480bd22b60ae339196c92918a8a984a9f05ac1a
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/202938
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
6 files changed