[clang] [Clang] VectorExprEvaluator::VisitCallExpr / InterpretBuiltin - Allow AVX512 VPSHUFBITQMB intrinsics to be used in constexpr (PR #168100)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon requested changes to this pull request.

Mainly a few style comments (applicable to both InterpBuiltin and ExprConstant implementations).

https://github.com/llvm/llvm-project/pull/168100