[llvm] [RISCV] Lower scalar `CLMUL` to `vclmul` if `clmul` instruction not available (PR #212616)

[Craig Topper via llvm-commits]

https://github.com/topperc commented:

We need to disable this when the NoImplicitFloat attribute is present. With that attribute we aren't allowed to use FP or vector registers if it isn't in the original source.

https://github.com/llvm/llvm-project/pull/212616