Fix ARM64 port after r22876.

src/compiler/arm64/linkage-arm64.cc

Index: src/compiler/arm64/linkage-arm64.cc
diff --git a/src/compiler/arm64/linkage-arm64.cc b/src/compiler/arm64/linkage-arm64.cc
index 72f6c55e0cc24195869350ddc210e5c0aa1f676c..240cef1e330e4ed5cf9cb567a59f151ac932f023 100644
--- a/src/compiler/arm64/linkage-arm64.cc
+++ b/src/compiler/arm64/linkage-arm64.cc
@@ -14,8 +14,6 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
-#if V8_TURBOFAN_TARGET
-
 struct LinkageHelperTraits {
   static Register ReturnValueReg() { return x0; }
   static Register ReturnValue2Reg() { return x1; }
@@ -64,7 +62,6 @@ CallDescriptor* Linkage::GetSimplifiedCDescriptor(
       zone, num_params, return_type, param_types);
 }
 
-#endif  // V8_TURBOFAN_TARGET
 }
 }
 }  // namespace v8::internal::compiler