[DAGCombiner] Remove code for optimizing select (xor Cond, 0), X, Y -> select...

[DAGCombiner] Remove code for optimizing select (xor Cond, 0), X, Y -> select Cond, X, Y. Just let combine on the xor itself take care of it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291534 91177308-0d34-0410-b5e6-96231b3b80d8