[X86][AVX512] Added support for lowering 512-bit vector shuffles to bit/byte shifts

512-bit VPSLLDQ/VPSRLDQ can only be used for avx512bw targets so lowerVectorShuffleAsShift had to be adjusted to include the subtarget

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272300 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed