[clang] [llvm] [Clang][RISCV] Move getVScaleRange logic into libLLVMFrontendDriver. NFC (PR #77327)

[Luke Lau via cfe-commits]

lukel97 wrote:

> I'm wondering if you considered moving the helper function into RISCVISAInfo?

Initially yes, but I ended up backing out of it since it would have been the only bit of "codegen" logic in RISCVISAInfo, and it seemed a shame to pollute it.

I also have a feeling that we will need to share more RISC-V specific driver logic between clang and flang eventually, e.g. the logic for `-mrvv-vector-bits` in Clang::AddRISCVTargetArgs. Although I would note that most targets don't need to move code into `libLLVMFrontendDriver`, RISC-V just happens to have quite a lot of RVV specific logic that isn't specific to C.



https://github.com/llvm/llvm-project/pull/77327