[llvm] [RISCV][NFC] refactor CFI emitting (PR #114227)

[Sam Elliott via llvm-commits]

lenary wrote:

> > LGTM
> 
> I've tried to make emitters for RVV [081ab88](https://github.com/llvm/llvm-project/commit/081ab881f4f84040d18536e3bfd2142fa1f7c1d2). However, I'm not sure that they make code more clear to be honest, maybe it would be better to leave `emitCalleeSavedRVVPrologCFI` and `emitCalleeSavedRVVPEpilogCFI` as they are.

I think I agree. I was happy enough without the emitters for RVV.

https://github.com/llvm/llvm-project/pull/114227