vboot: add errors for nvdata read/write failures

BUG=b:124141368, chromium:1006689
TEST=make clean && make runtests
BRANCH=none

Change-Id: Ieb47f54f665299b5377077c8975611ba3e1b8dc9
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1921775
Tested-by: Joel Kitching <kitching@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
1 file changed