[clang] [X86][AVX10.2] Replace nepbh with bf16 to match with others, NFCI (PR #134240)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

> are we missing clang codegen tests for these?

No, we don't generate these intrinsics. They will be transformed to llvm.fma ones.

https://github.com/llvm/llvm-project/pull/134240