[llvm] [RISCV] Override default sched policy (PR #115445)

[Luke Lau via llvm-commits]

lukel97 wrote:

Can you check that https://github.com/llvm/llvm-project/issues/107532 still spills? I have a feeling we still need to set microOpBufferSize otherwise latency always overrides register pressure

https://github.com/llvm/llvm-project/pull/115445