[Atomics] Remove Atomics code stubs; use TF ops

src/ppc/interface-descriptors-ppc.cc

Index: src/ppc/interface-descriptors-ppc.cc
diff --git a/src/ppc/interface-descriptors-ppc.cc b/src/ppc/interface-descriptors-ppc.cc
index 4a4075934e780ffe6181825980bd8c6fd0574e27..4dfb2bba662569cdd2ebd35d5fe11f4cd336ee93 100644
--- a/src/ppc/interface-descriptors-ppc.cc
+++ b/src/ppc/interface-descriptors-ppc.cc
@@ -420,15 +420,6 @@ void ResumeGeneratorDescriptor::InitializePlatformSpecific(
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
-
-void AtomicsLoadDescriptor::InitializePlatformSpecific(
-    CallInterfaceDescriptorData* data) {
-  Register registers[] = {
-      r4,  // the typedarray object
-      r3   // the index to load (untagged)
-  };
-  data->InitializePlatformSpecific(arraysize(registers), registers);
-}
 }  // namespace internal
 }  // namespace v8