[llvm] [RISCV] add load/store misched/PostRA cluster options (PR #149409)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave approved this pull request.

LGTM w/ minor comments

Please avoid force push unless necessary: https://llvm.org/docs/GitHub.html#rebasing-pull-requests-and-force-pushes

https://github.com/llvm/llvm-project/pull/149409