[clang] [clang][CodeGen] `sret` args should always point to the `alloca` AS, so use that (PR #114062)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

The reproducer I posted above still crashes, just in a different place.
```
clang-21: /home/jhuber/Documents/llvm/llvm-project/llvm/lib/IR/Instructions.cpp:744: void llvm::CallInst::init(llvm::FunctionType*, llvm::Value*, llvm::ArrayRef<llvm::Value*>, llvm::ArrayRef<llvm::OperandBundleDefT<llvm::Value*> >, const llvm::Twine&): Assertion `(i >= FTy->getNumParams() || FTy->getParamType(i) == Args[i]->getType()) && "Calling a function with a bad signature!"' failed.
```

https://github.com/llvm/llvm-project/pull/114062