mod_image_for_recovery: Learn partition map from image

Instead of relying on constants in chromeos-common.sh,
learn about partition mapping from the base image.

BUG=b:35045101
TEST=`mod_image_for_recovery --board=lasilla-sky` -> okboat

Change-Id: I0868f0dd7a6bdcfdcbb64f7d9d43006802adc9ef
Reviewed-on: https://chromium-review.googlesource.com/477974
Commit-Ready: Ian Coolidge <icoolidge@google.com>
Tested-by: Ian Coolidge <icoolidge@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed