[llvm] [Hexagon] Add lowering for `{max,min}num` (PR #202938)

[Nicolas Miller via llvm-commits]

npmiller wrote:

Doing a bit more digging it looks like `llvm.m{ax,in}num` were actually removed in favor of `llvm.m{ax,in}mumnum` in:

* https://github.com/llvm/llvm-project/pull/139056

There seem to have been some back and forth around the definition of these intrinsics, but the latest changes here:

* https://github.com/llvm/llvm-project/pull/172012

Add the following wording to [lang ref](https://llvm.org/docs/LangRef.html#llvm-minnum-intrinsic):

> The llvm.minnum intrinsic can be refined into llvm.minimumnum, as the latter exhibits a subset of behaviors of the former.

Which is what I based this patch on.

I'm a little unclear on why they were fully removed instead of kept back then though.

https://github.com/llvm/llvm-project/pull/202938