[turbofan] Use appropriate type for NodeId.

src/compiler/graph-reducer.cc

Index: src/compiler/graph-reducer.cc
diff --git a/src/compiler/graph-reducer.cc b/src/compiler/graph-reducer.cc
index 2164d1e7c505e291e261fb2f21e8e88b84e38238..5435fb072c6da4b7f81db9a77c2eddf8bac1c96f 100644
--- a/src/compiler/graph-reducer.cc
+++ b/src/compiler/graph-reducer.cc
@@ -140,7 +140,7 @@ void GraphReducer::ReduceTop() {
   }
 
   // Remember the max node id before reduction.
-  NodeId const max_id = graph()->NodeCount() - 1;
+  NodeId const max_id = static_cast<NodeId>(graph()->NodeCount() - 1);
 
   // All inputs should be visited or on stack. Apply reductions to node.
   Reduction reduction = Reduce(node);