[llvm] [AMDGPU] MCExpr-ify MC layer kernel descriptor (PR #80855)

[Fangrui Song via llvm-commits]

MaskRay wrote:

The BUILD_SHARED_LIBS=on linker error was due to library layerying violation. https://llvm.org/docs/CodingStandards.html#library-layering
AMDGPU/Utils/ cannot reference symbols defined in AMDGPU/MCTargetDesc.

https://github.com/llvm/llvm-project/pull/80855