Remove legacy EFM decoding tools from the project

[simoninns]

The efm-decode-* tools now completely replace the legacy ld-process-efm tools and there is no purpose to keep the old tools in the repo (other than backwards compatibility with scripts, etc.).

The new tools have been available for a while now - so the grace period is coming to an end. Also, having two tools is just confusing to end users.

Unless anyone has real objections (other than "I can't be bothered to re-write my decoding scripts") - I will generate a PR to remove the old tools shortly.

[simoninns]

With the latest PR ld-process-efm is now completely orphaned and removed from the CI/CD. The cross dependency from the AC3 tool has also been moved to the sub-moduled ezpwd library included by the new efm-process-* tools.

Next step will be to simply delete ld-process-efm from the repo completely.

[simoninns]

In the latest PR I have moved ld-process-efm into prototype/ (just as a holding position ready for deletion) - the tool is no long in the project cmake or CI/CD (although you can still make a local build if required).