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

[Shilei Tian via llvm-commits]

shiltian wrote:

> That is orthogonal to allowing 0 as min/max right?

That's 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.

At the moment only the upper bound can be skipped. `0` is a good value, as what you are doing right here.

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