[cleanup] Drop handwritten KeyedStoreIC code

src/ic/mips64/ic-compiler-mips64.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.
-
-#if V8_TARGET_ARCH_MIPS64
-
-#include "src/ic/ic.h"
-#include "src/ic/ic-compiler.h"
-
-namespace v8 {
-namespace internal {
-
-#define __ ACCESS_MASM(masm)
-
-
-void PropertyICCompiler::GenerateRuntimeSetProperty(
-    MacroAssembler* masm, LanguageMode language_mode) {
-  __ Push(StoreDescriptor::ReceiverRegister(), StoreDescriptor::NameRegister(),
-          StoreDescriptor::ValueRegister());
-
-  __ li(a0, Operand(Smi::FromInt(language_mode)));
-  __ Push(a0);
-
-  // Do tail-call to runtime routine.
-  __ TailCallRuntime(Runtime::kSetProperty);
-}
-
-
-#undef __
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_TARGET_ARCH_MIPS64