[llvm] [RISCV] Order stack objects by access density (PR #217507)

[via llvm-commits]

refuseno wrote:

> Looks good, but just a heads up was an LLM used to assist in this PR? If so it needs to be disclosed in the PR description per the AI policy

Yes, this PR was assisted by LLM. I've added disclosure in PR description. Thanks for reminder.

https://github.com/llvm/llvm-project/pull/217507