[llvm] Revert "[AMDGPU] Implement IR variant of isFMAFasterThanFMulAndFAdd (… (PR #145580)

[Jay Foad via llvm-commits]

jayfoad wrote:

> You don't need a PR for the revert. Just commit it directly, but do mention the reason to revert it.

... but then you committed this without mentioning the reason?

https://github.com/llvm/llvm-project/pull/145580