[llvm] [NFC][DirectX][SPIRV] Intrinsics should be defined the same (PR #110895)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

> Why does IntrWillReturn need to be removed from lerp?

because by switching `DefaultAttrsIntrinsic` `IntrWillReturn` is a default. `Intrinsic` didn't have any defaults. 

https://github.com/llvm/llvm-project/pull/110895