[llvm] [RISCV] Remove unnecessary patterns for tail agnostic FP intrinsics with rounding mode. (PR #94498)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Will you also fix the vsetvli insertion pass to recognize this undef pattern?

In #93796 we were actually planning on removing LiveIntervals at O0 which will make the codegen even more sub-optimal, but hopefully in exchange for faster compilation times. So if we're committing to that then I don't think this regression matters

https://github.com/llvm/llvm-project/pull/94498