[clang] [clang] Add GCC-compatible code model names for sparc64 (PR #79485)

[via cfe-commits]

koachan wrote:

`embmedany` is already rejected by the driver at the moment:
```
error: unsupported argument 'embmedany' to option '-mcmodel=' for target 'sparc64'
```

On the testing issue, however, would compiling LLVM with each of the code models + running codegen tests be enough to at least exercise the relevant parts (and see if there's still issues, etc.)?

https://github.com/llvm/llvm-project/pull/79485