[turbofan] Do not produce 2 ops for Int32AddWithOverflow.

It seems we produce both the usual add as well as the add with
overflow, when we should only generate the overflow variant. This
invalidates SSA assumptions in 2 tests (cctest/test-run-machops/RunInt32AddWithOverflowImm and
cctest/test-run-machops/RunInt64AddWithOverflowImm).

BUG=

Review URL: https://codereview.chromium.org/1757213003

Cr-Commit-Position: refs/heads/master@{#34507}

src/compiler/x64/instruction-selector-x64.cc

@@ -1785,7 +1785,7 @@ void InstructionSelector::VisitWord64Equal(Node* const node) {
 void InstructionSelector::VisitInt32AddWithOverflow(Node* node) {
   if (Node* ovf = NodeProperties::FindProjection(node, 1)) {
     FlagsContinuation cont = FlagsContinuation::ForSet(kOverflow, ovf);
-    VisitBinop(this, node, kX64Add32, &cont);
+    return VisitBinop(this, node, kX64Add32, &cont);
   }
   FlagsContinuation cont;
   VisitBinop(this, node, kX64Add32, &cont);