[llvm] [RISCV] Remove {s,u}int_to_fp custom op action for f16/bf16 (PR #111471)

[Luke Lau via llvm-commits]

lukel97 wrote:

> > Since the affected test is for a type that will crash when lowering because it's > LMUL 8 and we don't split fixed length f16/bf16 vectors, I'm not too worried that the cost of it has increased.
> 
> Doesn't the type legalizer split them? Or do you mean we don't split before promoting?

The type legalizer splits them, but when we do our own promotion for {s,u}int_to_fp via custom lowering we only check for scalable vector types in `isPromotedOpNeedingSplit`

https://github.com/llvm/llvm-project/pull/111471