futility: Remove --devsign and --devkeyblock

This feature has not been needed since pre-2012 devices which have long
since reached their end of life. We can safely remove it to simplify the
code.
Also remove ZGB image, as it is no longer needed.

BUG=b:197114807
TEST=sudo FEATURES=test emerge vboot_reference
BRANCH=none

Signed-off-by: Jakub Czapiga <jacz@semihalf.com>
Cq-Depend: chromium:3650757
Change-Id: I889dc6300c5cb72bdfcb9c2b66d63e97d3f8c862
Disallow-Recycled-Builds: test-failures
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3578968
Commit-Queue: Jakub Czapiga <czapiga@google.com>
Auto-Submit: Jakub Czapiga <czapiga@google.com>
Tested-by: Jakub Czapiga <czapiga@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
17 files changed