Use std::atomic

Replace amd::Atomic with std::atomic. Remove make_atomic uses by
converting the variable to std::atomic and making sure the memory
order is relaxed when synchronizes-with is not needed.

Delete utils/atomic.hpp.

Change-Id: I0b36db8d604a8510ac6e36b32885fd16a1b8ccfa

rocclr/thread/monitor.cpp

@@ -19,11 +19,11 @@
  THE SOFTWARE. */
 
 #include "thread/monitor.hpp"
-#include "thread/atomic.hpp"
 #include "thread/semaphore.hpp"
 #include "thread/thread.hpp"
 #include "utils/util.hpp"
 
+#include <atomic>
 #include <cstring>
 #include <tuple>
 #include <utility>