[llvm] [IR][NFC] Update magic number to meaningful hash value. (PR #98416)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

Did you run `ninja check-llvm` with this change applied?

The values are "arbitrary" because `MergeFunctions` will change its output order depending upon the function hash. The values were set to preserve the ordering of existing test cases.

The custom `constexpr` hash seems a bit hacky and doesn't provide anything over what exists currently (and slightly increased compile times). Refactoring to use constants defined at the top of the file I'm also not sure helps readability significantly given the comments.

https://github.com/llvm/llvm-project/pull/98416