futility: add support for usbpd1 images

The USB Type-C chargers released with Samus ("Pixel (2015)") have
upgradable firmware. Those firmware images are currently signed
by some custom scripts. This adds support for those images to
futility, so that those custom scripts can be replaced.

Note that due to space considerations, the usbpd firmware images
don't have room for handy things like an FMAP or headers for the
signatures. Accordingly, all the normally variable factors (image
size, signature algorithms, etc.) are hard coded and the image
itself just looks like a bunch of random numbers. Because of

1. There's no way to recognize this type of file, and nothing to
   display about it.

2. You have to give the "--type usbpd1" arg to the sign command.

3. I'm designating this file type "v1" because I hope that the
   firmware for any future adapters will be more readily

TEST=make runtests

This adds a new test that signs usbpd1 firmware images using
futility, and compares the result to the same files signed by the
custom scripts, ensuring that they are bitwise identical.

Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Change-Id: Idbe061db5b3c8e474ada47b40bcbe04bbecdba3a
Reviewed-on: https://chromium-review.googlesource.com/262899
Reviewed-by: Randall Spangler <rspangler@chromium.org>
22 files changed