[InstCombine] Remove unreachable code for turning an And where all demanded bits...

[InstCombine] Remove unreachable code for turning an And where all demanded bits on both sides are known to be zero into a constant 0.

We already handled a superset check that included the known ones too and folded to a constant that may include ones. But it can also handle the case of no ones.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300093 91177308-0d34-0410-b5e6-96231b3b80d8