[clang] [clang][CodeGen] Remove unnecessary ShouldLinkFiles conditional (PR #96951)

[Lei Huang via cfe-commits]

lei137 wrote:

I'm getting a build failure with `-Werror` on powerpc from this:
```
~llvm-project/clang/lib/CodeGen/LinkInModulesPass.cpp:24:19: error: field 'ShouldLinkFiles' is uninitialized when used here [-Werror,-Wuninitialized]
4073    24 |   ShouldLinkFiles(ShouldLinkFiles) {}
4074       |                   ^
```

https://github.com/llvm/llvm-project/pull/96951