update_program_fw: Add support for ambassador firmware

Ambassador has the same set of packages to emerge as Puff.

BUG=none
TEST=ran ambassador upgrade

Change-Id: Iafbe9a1ed2db22abbc43c513d8e78cd2b332bb97
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2590061
Tested-by: Matthew Ziegelbaum <ziegs@chromium.org>
Commit-Queue: Andrew McRae <amcrae@chromium.org>
Auto-Submit: Matthew Ziegelbaum <ziegs@chromium.org>
Reviewed-by: Andrew McRae <amcrae@chromium.org>