[clang] [CIR]Fix failing my_fmaxf test (PR #180956)

[Andrzej Warzyński via cfe-commits]

banach-space wrote:

Why not make sure that _with_ and _without_ `-fclangir` LLVM IR will include the `nsz` flag: 
```mlir
call nsz float @llvm.maxnum.f32
```
? Given the complexity of Clang and C-like-lang compilation, this sort of subtle changes are likely to be tricky to track and fix in the future. Just my 2p.

https://github.com/llvm/llvm-project/pull/180956