[llvm] [DirectX][SimplifyCFG] Don't narrow to i8 arrays for switch tables (PR #203103)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

HLSL failure is because this change fixes the  validation issue on the offload tests

```
Unexpectedly Passed Tests (1):
  OffloadTest-clang-mtl :: WaveOps/WaveReadLaneAt.index.test
```

https://github.com/llvm/llvm-project/pull/203103