image_signing: make_dev_ssd.sh: convert to info/error helpers
image_signing: make_dev_ssd.sh: convert to info/error helpers

This makes the output easier to follow when multiple scripts are being run.

BRANCH=None
BUG=chromium:714598
TEST=signing images still works

Change-Id: I96e20f38b6a51ad4dc8064fa3fb3d4302c47888f
Reviewed-on: https://chromium-review.googlesource.com/497302
Commit-Ready: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: David Riley <a1c52a99f156ff41f0ea478f29291144551a02f6@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot