[llvm] [AMDGPU] Change expand-fp opt level argument syntax (PR #157408)

[Frederik Harwath via llvm-commits]

frederik-h wrote:

> Should `O2` and `O3` also show up in some test?

Thanks for the suggestion! I have now added a test covering the pass parameter parsing explicitly. I am not sure if we need to cover `O2` and `O3` in, say, llvm/test/Transforms/ExpandFp/AMDGPU/frem.ll. The pass does only distinguish between `O0` and `O1` so far. @arsenm?

https://github.com/llvm/llvm-project/pull/157408