fw update: library to create pldm fw package

Implement some helper functions to easily create a pldm fw package in a
few lines of user code.

This is helpful for unit testing the code update flow.

fw update: library to create pldm fw package

Implement some helper functions to easily create a pldm fw package in a
few lines of user code.

This is helpful for unit testing the code update flow.

The package created is for testing purpose. The library is not
fully-featured or complete and should not be relied upon for anything
other than the tests in this repo.

https://github.com/openbmc/docs/blob/master/designs/code-update.md

Tested: next few patches in series

Change-Id: If899e5537a2e5ac641544ca80e8876d83549da28
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>

show more ...