[clang] [clang][OpenCL][CodeGen][AMDGPU] Do not use `private` as the default AS for when `generic` is available (PR #112442)

[Alex Voicu via cfe-commits]

AlexVlx wrote:

> LLVM Buildbot has detected a new failure on builder `openmp-offload-amdgpu-runtime` running on `omp-vega20-0` while building `clang` at step 7 "Add check check-offload".
> 
> Full details are available at: https://lab.llvm.org/buildbot/#/builders/30/builds/8694
> 
> Here is the relevant piece of the build log for the reference

@jhuber6 apologies for the ping but any idea why a pure OCL change would trigger a failure in our OMP offload RT?

https://github.com/llvm/llvm-project/pull/112442