Fix clippy::precedence warning in current beta

[jannic]

With current beta (1.85.0-beta.1), rustc introduced new clippy warnings regarding non-obvious operator precedence:

warning: operator precedence can trip the unwary
   --> src/adc.rs:876:14
    |
876 |         Self(1 << pins.0.channel() | 1 << pins.1.channel())
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider parenthesizing your expression: `(1 << pins.0.channel()) | (1 << pins.1.channel())`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#precedence
    = note: `#[warn(clippy::precedence)]` on by default

These can be easily fixed by adding some parentheses, as shown in this pull request.

I'm not sure if this really helps readability. Alternatively, we could silence clippy for this warning. (#[allow(clippy::precedence)])

[jonathanpallant]

This is definitely better