[llvm] [Scalarizer][DirectX] support structs return types (PR #111569)

[Mariusz Sikora via llvm-commits]

mariusz-sikora-at-amd wrote:

At the beginning I thought that this is AMDGPU specific issue, but I also build AArch64 and used existing test and it failed also. This test is running `llc` so `ScalarizerPass` is not called, but `uadd.with.overflow` is used.

```
./bin/opt -mtriple=aarch64-none-linux-gnu  -passes='function(scalarizer)' ../llvm/test/CodeGen/AArch64/vec_uaddo.ll -S 
```

https://github.com/llvm/llvm-project/pull/111569