[llvm] Revert "[GlobalISel] Add support for lowering byref attribute" (PR #96784)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> "Theoretically AMDGPU should need this for the GlobalISel kernel lowering path"

But it doesn't because we completely bypass the normal argument legalization and directly lower from the IR signature for kernels

> Shouldn't by ref be used in all the cases in which a parameter is passed by reference? 

No. Byref is rarely used, and doesn't imply any code generation requirement in the callee. In the AMDGPU usage we just need to know the allocated size from the byref attribute 



https://github.com/llvm/llvm-project/pull/96784