[llvm] [GlobalISel] Add support for lowering byref attribute (PR #96733)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> For test cases, I'd like to hear your suggestions.

Theoretically AMDGPU should need this for the GlobalISel kernel lowering path. I'd need to look to see how this was avoided 

https://github.com/llvm/llvm-project/pull/96733