[llvm] [KnownFPClass] Add neg_square and fma_neg_square (PR #227248)

[via llvm-commits]

s-mv wrote:

I'm not including cases that fold regardless of the change, for example:
```
define i1 @temp(float nofpclass(nan) %x) {
  %neg = fneg float %x
  %m = fmul float %neg, %x
  %n = fneg float %m
  %r = call i1 @llvm.is.fpclass.f32(float %n, i32 60)
  ret i1 %r
}
```
(this becomes false regardless)

https://github.com/llvm/llvm-project/pull/227248