Fix MIPS build: use stubbed-out TF implementation

src/compiler/linkage.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/linkage.h"
 
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/node.h"
 #include "src/compiler/pipeline.h"
@@ skipping 112 matching lines @@
 
 CallDescriptor* Linkage::GetStubCallDescriptor(
     CodeStubInterfaceDescriptor* descriptor, int stack_parameter_count) {
   UNIMPLEMENTED();
   return NULL;
 }
 
 
 CallDescriptor* Linkage::GetSimplifiedCDescriptor(
     Zone* zone, int num_params, MachineRepresentation return_type,
-    MachineRepresentation* param_types) {
+    const MachineRepresentation* param_types) {
   UNIMPLEMENTED();
   return NULL;
 }
 #endif  // !V8_TURBOFAN_TARGET
 }
 }
 }  // namespace v8::internal::compiler