Fix a compiler warnings in timers.c that was caused by casting a valu…

[RichardBarry]

Description

Fix a compiler warnings in timers.c that was caused by casting a value to an 8-bit type before its bits were inverted, rather than after.

Test Steps

Compile the code using Visual Studio to see the warnings before applying this PR.

Checklist:

• [ ] I have tested my changes. No regression in existing tests. I tested compilations in Visual Studio and GCC. Please also compile using IAR.

• [ ] I have modified and/or added unit-tests to cover the code changes in this Pull Request. This is a compile time check.

Related Issue

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.8% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.00%. Comparing base (d95451d) to head (6acaa2f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1010 +/- ## ======================================= Coverage 93.00% 93.00% ======================================= Files 6 6 Lines 3200 3200 Branches 879 879 ======================================= Hits 2976 2976 Misses 111 111 Partials 113 113 ``` | [Flag](https://app.codecov.io/gh/FreeRTOS/FreeRTOS-Kernel/pull/1010/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FreeRTOS) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/FreeRTOS/FreeRTOS-Kernel/pull/1010/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FreeRTOS) | `93.00% <100.00%> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FreeRTOS#carryforward-flags-in-the-pull-request-comment) to find out more.

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