[llvm] Revert "LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (#112852)" (PR #168838)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> The point is since all targets share the same defination, a change on that needs consensus made through all targets. The hardware details (especially there are differences among different targets) are not the only consideration for the defination. And I explained them in details in the following 2 bullets.

This has been discussed at length in the previous threads, and this has never worked correctly across all targets. The operation you want is minimumnum 

https://github.com/llvm/llvm-project/pull/168838