[llvm] [LLVM][Parser] Check invalid overload suffix for intrinsics (PR #108315)

[Rahul Joshi via llvm-commits]

jurahul wrote:

The problem I ran into was literally this: I was writing a unit test using overloaded intrinsics and observed that no one complained if I messed up the mangling suffix (use .f16 for a float variant for instance), and that motivated this change. 

I am actually not sure what happens if in C++ someone creates a Function::Create() to create an intrinsic decl but with bad overload suffix. I'd expect that to be strict, not sure if it is.

https://github.com/llvm/llvm-project/pull/108315