Revert "Add new atomic operations and use them in two places."

runtime/vm/atomic.h

Index: runtime/vm/atomic.h
diff --git a/runtime/vm/atomic.h b/runtime/vm/atomic.h
index edf1990fe13585dfac659f90a82c272b6e4bd2d2..b6e5f280001ae5f61fa3c8e10d339f9a91de478d 100644
--- a/runtime/vm/atomic.h
+++ b/runtime/vm/atomic.h
@@ -60,10 +60,6 @@ class AtomicOperations : public AllStatic {
   static intptr_t LoadRelaxedIntPtr(intptr_t* ptr) {
     return *static_cast<volatile intptr_t*>(ptr);
   }
-
-  template<typename T> static T LoadAcquire(T* ptr);
-
-  template<typename T> static void StoreRelease(T* ptr, T val);
 };