[llvm] [AMDGPU] Fix maximum physical LDS reporting for gfx6 (PR #223185)

[Chinmay Deshpande via llvm-commits]

chinmaydd wrote:

Thanks. Some of this work started with the reconciliation of Comgr's isa-metadata.def file, so we'd like to get these right. Not sure how much of it matters for gfx6... but trying to ensure the AMDGPU backend remains the historical source of truth.

https://github.com/llvm/llvm-project/pull/223185