[TargetFolder] Use DL-aware folding for icmp

The Fold() call was accidentally dropped in
138fcc5f76, though it doesn't seem
to make a difference in practice (no test changes).

llvm/include/llvm/Analysis/TargetFolder.h

@@ -103,7 +103,7 @@ public:
     auto *LC = dyn_cast<Constant>(LHS);
     auto *RC = dyn_cast<Constant>(RHS);
     if (LC && RC)
-      return ConstantExpr::getCompare(P, LC, RC);
+      return Fold(ConstantExpr::getCompare(P, LC, RC));
     return nullptr;
   }