[Atomics] Remove Atomics code stubs; use TF ops

src/compiler/instruction-scheduler.cc

Index: src/compiler/instruction-scheduler.cc
diff --git a/src/compiler/instruction-scheduler.cc b/src/compiler/instruction-scheduler.cc
index d36d8b7715174cb01c04a5fb94045b555d62baf9..9bff4f96e6dd96b2e3fd64f609f41c8cf4ec17fb 100644
--- a/src/compiler/instruction-scheduler.cc
+++ b/src/compiler/instruction-scheduler.cc
@@ -254,6 +254,13 @@ int InstructionScheduler::GetInstructionFlags(const Instruction* instr) const {
     case kArchStoreWithWriteBarrier:
       return kHasSideEffect;
 
+    case kAtomicLoadInt8:
+    case kAtomicLoadUint8:
+    case kAtomicLoadInt16:
+    case kAtomicLoadUint16:
+    case kAtomicLoadWord32:
+      return kIsLoadOperation;
+
 #define CASE(Name) case k##Name:
     TARGET_ARCH_OPCODE_LIST(CASE)
 #undef CASE