[SelectionDAG] Fix copy/paste mistake in SDNodeFlags::intersectWith

The NonNeg flag was being Anded with the Exact flag.

Author: topperc

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -454,7 +454,7 @@ struct SDNodeFlags {
     NoUnsignedWrap &= Flags.NoUnsignedWrap;
     NoSignedWrap &= Flags.NoSignedWrap;
     Exact &= Flags.Exact;
-    NonNeg &= Flags.Exact;
+    NonNeg &= Flags.NonNeg;
     NoNaNs &= Flags.NoNaNs;
     NoInfs &= Flags.NoInfs;
     NoSignedZeros &= Flags.NoSignedZeros;