vboot/sign_official_build: merge ssd+base and remove usb

Merge aliases "ssd" and "base", since they do the same thing but
only "base" is used in chromite scripts.

Remove "usb" since it is not used anywhere.

BUG=b:188121855
TEST=make clean && make runtests
BRANCH=none

Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: Ief610387fc1b6d72fe8674b0e4d51d74e6173ddd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2989637
Tested-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Joel Kitching <kitching@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
1 file changed