[clang] [CIR][AArch64] Lower BF16 vduph lane builtins (PR #185852)

[Jiahao Guo via cfe-commits]

E00N777 wrote:

@banach-space 
I've updated the patch accordingly: narrowed the lowering to the two BF16 `vduph_*` builtins, restored the case order, and moved the tests into `neon/bf16-getset.c`. I've also removed the ported cases from the old test file.


https://github.com/llvm/llvm-project/pull/185852