Fix rom::crc docs

[jordanhalase]

Must

• The code compiles without errors or warnings. Docs-only change
• All examples work.
• cargo fmt was run.
• Your changes were added to the CHANGELOG.md in the proper section. N/A unless told it's needed
• You updated existing examples or added examples (if applicable).
• Added examples are checked in CI

Nice to have

• You add a description of your work to this PR.
• You added proper docs for your newly added features and code.

I noticed cargo-fmt was mangling the docs.

I also noticed a few typos.

[jessebraham]

Thanks!