[cleanup] Drop handwritten KeyedStoreIC code

src/ic/s390/ic-compiler-s390.cc

-// Copyright 2015 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_S390
-
-#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) {
-  __ mov(r0, Operand(Smi::FromInt(language_mode)));
-  __ Push(StoreDescriptor::ReceiverRegister(), StoreDescriptor::NameRegister(),
-          StoreDescriptor::ValueRegister(), r0);
-
-  // Do tail-call to runtime routine.
-  __ TailCallRuntime(Runtime::kSetProperty);
-}
-
-#undef __
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_TARGET_ARCH_S390