[X86][AVX512] Improve vector rotation constant folding tests

Test constant folding both on node creation (which already works) and once the input nodes have been folded themselves (not working yet).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308611 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed