Fix #2391, add cfe to prefix list for msgids.h and platform_cfg.h

[jphickey]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
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Describe the contribution
This allows the script to pick up the file if it was named simply "cfe_msgids.h" or "cfe_platform_cfg.h", rather than insisting it be named with a platform-specific prefix

Fixes #2391

Testing performed
Build and run with stakeholder configuration

Expected behavior changes
A file named cfe_msgids.h is picked up by the build system, as expected.

System(s) tested on
Debian

Contributor Info - All information REQUIRED for consideration of pull request
Joseph Hickey, Vantage Systems, Inc.