[llvm] [DirectX] Preserve value names in DXILOpLowering. NFC (PR #108089)

[Justin Bogner via llvm-commits]

bogner wrote:

> Yep.. names looked preserved. So the CHECK: tests are looking for anything now when before they looked for any number?

Correct. I don't think we can actually check that the names match the input names because there are configs where all value names get dropped.

https://github.com/llvm/llvm-project/pull/108089