[llvm] [AMDGPU][Attributor] Make `AAAMDFlatWorkGroupSize` honor existing attribute (PR #114357)

[John Tramm via llvm-commits]

jtramm wrote:

Ah, interesting! Which file(s) should I be converting to `.ll`? And how do I remove attributes in a `.ll` file -- just delete the entire line or change to something else? Any specific commands to give to `llvm-dis` for converting between file types?

https://github.com/llvm/llvm-project/pull/114357