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/device/gpu/gpuresource.cpp

@@ -34,7 +34,6 @@
 #include "device/gpu/gpudevice.hpp"
 #include "device/gpu/gpublit.hpp"
 #include "device/gpu/gputimestamp.hpp"
-#include "thread/atomic.hpp"
 #include "hsa_ext_image.h"
 
 #include <string>