docs: minor fixes for creating kernel modules doco

[michael-robbins]

Pull Request

What? (description)

Minor fixes for command and examples in the new kernel-module doco.

Why? (reasoning)

Just running through it myself and found a couple of small nits :)

Acceptance

Please use the following checklist:

• [ ] you linked an issue (if applicable)
• [ ] you included tests (if applicable)
• [ ] you ran conformance (make conformance)
• [ ] you formatted your code (make fmt)
• [ ] you linted your code (make lint)
• [ ] you generated documentation (make docs)
• [ ] you ran unit-tests (make unit-tests)

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