[Bug] Fix unused variable error when using ChibiOS Bitbang serial driver

[drashna]

Description

The bitbang serial driver for chibiOS doesn't compile, currently. (shows how often it is used)

Specifically, #16023 removed this line of code, which is the only place that checksum received was being called in that function.

    *trans->status = (checksum_computed == checksum_received) ? TRANSACTION_ACCEPTED : TRANSACTION_DATA_ERROR;

This removes the variable and just calls the function, "fixing" the error.

Types of Changes

• Core
• Bugfix

Issues Fixed or Closed by This PR

• reddit

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[drashna]

@KarlK90 since it was your PR that changed it

[KarlK90]

The mechanism of the secondary side to not accept data that was transmitted should the checksums mismatch is not implemented in the current split comms algorithm. So I think it is just save to remove this last piece and not implement anything else instead.

Both the main and secondary side could early return if the computed and received checksums mismatch, but given the low adoption maybe this could just stay as it is. (Maybe there are unknown side-effects to early returning)