[clang-tools-extra] [clang-tidy] Fix readability-simplify-boolean-expr for init statements (PR #172220)

[via cfe-commits]

https://github.com/zeyi2 requested changes to this pull request.

The majority of the fix looks good. Thanks for the fix!

However, you still need to document the changes in [ReleaseNotes.rst, Changes in existing checks](https://github.com/llvm/llvm-project/blob/72f3995363eb7fe01df4eb54b3abb6cef3ee1568/clang-tools-extra/docs/ReleaseNotes.rst?plain=1#L351). Please remember to keep the alphabetical order :)

https://github.com/llvm/llvm-project/pull/172220