[AVX-512] Add unmasked version of shift by immediate and shift by single element...

[AVX-512] Add unmasked version of shift by immediate and shift by single element in XMM.

Summary:
This is the first step towards being able to add the avx512 shift by immediate intrinsics to InstCombineCalls where we aleady support the sse2 and avx2 intrinsics. We need to the unmasked versions so we can avoid having to teach InstCombineCalls that it would need to insert selects sometimes. Instead we'll just add the selects around the new instrinsics in the frontend.

This change should also enable the shift by i32 intrinsics to take a non-constant shift value just like the avx2 and sse intrinsics. This will enable us to fix PR30691 once we update clang.

Next I'll switch clang to use the new builtins. Then we'll come back to the backend and remove/autoupgrade the old intrinsics. Then I'll work on the same series for variable shifts.

Reviewers: RKSimon, zvi, delena

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D26333

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286711 91177308-0d34-0410-b5e6-96231b3b80d8