[llvm] [AMDGPU] Allow 0 as min./max. of amdgpu-waves-per-eu (PR #138284)

[Lucas Ramirez via llvm-commits]

lucas-rami wrote:

> Can we instead disallow using just one value?

That is orthogonal to allowing 0 as min/max right? One may still want to specify only a minimum or a maximum, so we need a way to say "don't care" for the other bound. I could disallow specifying only one value in a follow-up PR if there is agreement there, though I am not sure of what additional precaution to take for changes that will make some existing user code fail to compile.

https://github.com/llvm/llvm-project/pull/138284