Use git submodule to pull in cryptoauthlib

[troth]

Instead of committing the code for cryptoauthlib (which is essentially a fork), remove the committed code and include the cryptoauthlib project as a git submodule.

Now that cryptoauthlib has been provided as a github project (https://github.com/MicrochipTech/cryptoauthlib), it really doesn't make sense to have all of the code from cryptoauthlib committed into this project.

[bryan-hunt]

It's on the roadmap when the requisite changes are merged to mainline. That is a while out.