[llvm] [X86] Clear regcall arg aliases in dynamic CSR masks (PR #225262)

[Demetrios Chiuratto Agourakis via llvm-commits]

agourakis82 wrote:

Acknowledging the first-time contributor note and the LLVM AI Tool Use Policy:

- There is a human in the loop for every change here (me).
- I reviewed the diffs before opening each PR and can answer questions about the motivation, root cause, and implementation during review.
- PR descriptions now include an explicit AI-assistance disclosure.

Happy to adjust anything reviewers want tightened.

https://github.com/llvm/llvm-project/pull/225262