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


[ROCm/clr commit: 5d4b6f74d3]

projects/clr/rocclr/device/devprogram.cpp

@@ -30,6 +30,7 @@
 #include "comgrctx.hpp"
 
 #include <algorithm>
+#include <atomic>
 #include <cstdio>
 #include <fstream>
 #include <iostream>
@@ -1345,7 +1346,7 @@ bool Program::initBuild(amd::option::Options* options) {
   programOptions_ = options;
 
   if (options->oVariables->DumpFlags > 0) {
-    static amd::Atomic<unsigned> build_num = 0;
+    static std::atomic<uint> build_num{0};
     options->setBuildNo(build_num++);
   }
   buildLog_.clear();