[clang] [HIP] Replace use of `llvm-mc` with `clang` (PR #112041)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > I fixed an apparent missing test dependency in [1ac6ef5](https://github.com/llvm/llvm-project/commit/1ac6ef5af28b72e534496a9833a2b75a2aba66cc) and this commit removed the llvm-mc dependency
> 
> I probably should've remembered to include removing that in this patch.

I think some other hexagon code is also using llvm-mc 

https://github.com/llvm/llvm-project/pull/112041