Clean up some A64 specific code in common code that was introduced by A64 merge

src/a64/simulator-a64.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 236 matching lines @@
       type_ = X_ARG;
     }
 
     explicit CallArgument(double argument) {
       ASSERT(sizeof(argument) == sizeof(bits_));
       memcpy(&bits_, &argument, sizeof(argument));
       type_ = D_ARG;
     }
 
     explicit CallArgument(float argument) {
-      TODO_UNIMPLEMENTED("CallArgument(float) is untested.");
+      // TODO(all): CallArgument(float) is untested, remove this check once
+      //            tested.
+      UNIMPLEMENTED();
       // Make the D register a NaN to try to trap errors if the callee expects a
       // double. If it expects a float, the callee should ignore the top word.
       ASSERT(sizeof(kFP64SignallingNaN) == sizeof(bits_));
       memcpy(&bits_, &kFP64SignallingNaN, sizeof(kFP64SignallingNaN));
       // Write the float payload to the S register.
       ASSERT(sizeof(argument) <= sizeof(bits_));
       memcpy(&bits_, &argument, sizeof(argument));
       type_ = D_ARG;
     }
 
@@ skipping 588 matching lines @@
   static void UnregisterCTryCatch() {
     Simulator::current(Isolate::Current())->PopAddress();
   }
 };
 
 #endif  // !defined(USE_SIMULATOR)
 
 } }  // namespace v8::internal
 
 #endif  // V8_A64_SIMULATOR_A64_H_