[clang] [clang][X86] Allow VALIGND/Q element-shift intrinsics in constexpr evaluation (PR #168206)

[Simon Pilgrim via cfe-commits]

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

One final clang-format fix (I removed the unnecessary const but there's still an indentation issue)

https://github.com/llvm/llvm-project/pull/168206