[clang] [llvm] [SPIRV] Add OpInf support for isinf hlsl intrinsic (PR #156570)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

Is there some reason clang can't just generate a call to `llvm.is.fpclass`?

https://github.com/llvm/llvm-project/pull/156570