[llvm] [RISCV] Separate more of scalar FP in CC_RISCV. NFC (PR #107908)

[Alex Bradbury via llvm-commits]

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

Nice cleanup, thanks. I also kicked the tires with the GCC torture suite across a few configs and saw no codegen changes (as expected, given this intends to be NFC).

https://github.com/llvm/llvm-project/pull/107908