[clang] [Headers][X86] Enable constexpr handling for MMX/SSE/AVX/AVX512 PMADDWD/PMADDUBSW intrinsics (PR #161563)

[Simon Pilgrim via cfe-commits]

RKSimon wrote:

Best way is just to use the Update button like I just did - it'll trigger fresh CI builds

https://github.com/llvm/llvm-project/pull/161563