[stubs] Drop CallApiCallbackStub::call_data_undefined optimization.

src/mips64/code-stubs-mips64.cc

Index: src/mips64/code-stubs-mips64.cc
diff --git a/src/mips64/code-stubs-mips64.cc b/src/mips64/code-stubs-mips64.cc
index 4a0e51a1d45ceb17888284ce0e534828024accbc..1b6b5025226c77253c30694bf551a337305f204f 100644
--- a/src/mips64/code-stubs-mips64.cc
+++ b/src/mips64/code-stubs-mips64.cc
@@ -2976,9 +2976,7 @@ void CallApiCallbackStub::Generate(MacroAssembler* masm) {
   }
 
   Register scratch = call_data;
-  if (!call_data_undefined()) {
-    __ LoadRoot(scratch, Heap::kUndefinedValueRootIndex);
-  }
+  __ LoadRoot(scratch, Heap::kUndefinedValueRootIndex);
   // Push return value and default return value.
   __ Push(scratch, scratch);
   __ li(scratch, Operand(ExternalReference::isolate_address(masm->isolate())));