[NewGVN] Don't derive incorrect implications.

In the testcase attached,  we believe %tmp1 implies %tmp4.
where:
  br i1 %tmp1, label %bb2, label %bb7
  br i1 %tmp4, label %bb5, label %bb7

because Wwhile looking at PredicateInfo stuffs we end up calling
isImpliedTrueByMatchingCmp() with the arguments backwards.

Differential Revision:  https://reviews.llvm.org/D32718

llvm-svn: 301849