AVX-512: Scalar ERI intrinsics

AVX-512: Scalar ERI intrinsics
including SAE mode and memory operand.
Added AVX512_maskable_scalar template, that should cover all scalar instructions in the future.

The main difference between AVX512_maskable_scalar<> and AVX512_maskable<> is using X86select instead of vselect.
I need it, because I can't create vselect node for MVT::i1 mask for scalar instruction.

http://reviews.llvm.org/D6378

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222820 91177308-0d34-0410-b5e6-96231b3b80d8