Call cgraph_get_node rather than cgraph_node.

This is for a recent change to the gcc middle-end.

From-SVN: r172335

gcc/go/gofrontend/gogo-tree.cc

@@ -401,7 +401,7 @@ Gogo::write_initialization_function(tree fndecl, tree init_stmt_list)
   gimplify_function_tree(fndecl);
 
   cgraph_add_new_function(fndecl, false);
-  cgraph_mark_needed_node(cgraph_node(fndecl));
+  cgraph_mark_needed_node(cgraph_get_node(fndecl));
 
   current_function_decl = NULL_TREE;
   pop_cfun();