Correct some Clippy lints

[Tudyx]

When executing clippy in the root directory with this command

fd Cargo.toml --exec cargo clippy --manifest-path

It finds some clippy lints, if you find it useful maybe we could correct some of them. Of course they are some which are legitimate like when explicitly set an address to u64 instead of usize because we want to support only x86_64.

[Carl Fredrik Samson]

As commented in the other issue, I try to avoid project-wide changes that make the code deviate from the book (even though it's an improvement). If the book ever gets a second edition, it seems natural to attend to the clippy lints wherever it makes sense (some of the suggestions are good, but others corrects something that's intentionally written that way).

[Tudyx]

That's makes sense, thank you for your answer