[AMDGPU][Clang] use ScopeModel to translate integer scopes [NFC] (#198250)
The assumption here is that AMDGPU builtins (typically suffixed with
`__builtin_amdgcn`) use the `__MEMORY_SCOPE_*` enumeration, and not the
`__HIP_MEMORY_SCOPE_*` enumeration (which is how it should be).
Assisted-By: Claude Opus 4.6