X86 Tests: Add AVX512BW config to CodeGenPrepare test. NFC

Case points out that we don't consider shifts supported by AVX512BW
in isVectorShiftByScalarCheap()

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323242 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed