[clang] [HLSL] Fix resource wrapper declaration (PR #125718)

[Steven Perron via cfe-commits]

s-perron wrote:

> 2\. It feels wrong to do this in CodeGen. It seems like we should be identifying an appropriate storage class in Sema such that we assign the correct linkage automatically.

If we change the storage class in Sema, then codegen is not able to distinguish between:

```
static RWBuffer<int4> s;
RWBuffer<int4> global;
```

This causes problems during codegen because the resource init function is created only for the "global" variables, and not static. We could probably refactor that to make it work. Just be aware that it might be a bigger change than you might expect.

https://github.com/llvm/llvm-project/pull/125718