[llvm] fix `llvm.fma.f16` double rounding issue when there is no native support (PR #171904)

[Folkert de Vries via llvm-commits]

folkertdev wrote:

I don't want to add to those tests, but they fail because on some platforms the output is now different. So the output needs to be updated, but the standard `llvm-lit` won't even run this test.

https://github.com/llvm/llvm-project/pull/171904