remove the _ready flag in ihipStreamCallback_t and the mutex that protects it.

src/hip_hcc.cpp

@@ -1445,10 +1445,6 @@ hipError_t ihipStreamSynchronize(hipStream_t stream) {
 void ihipStreamCallbackHandler(ihipStreamCallback_t* cb) {
     hipError_t e = hipSuccess;
 
-    // Notify hipStreamAddCallback that callback handler thread is active
-    std::lock_guard<std::mutex> guard(cb->_mtx);
-    cb->_ready = true;
-
     // Synchronize stream
     tprintf(DB_SYNC, "ihipStreamCallbackHandler wait on stream %s\n",
             ToString(cb->_stream).c_str());

src/hip_hcc_internal.h

@@ -620,13 +620,10 @@ class ihipStreamCallback_t {
    public:
     ihipStreamCallback_t(hipStream_t stream, hipStreamCallback_t callback, void* userData)
         : _stream(stream), _callback(callback), _userData(userData) {
-        _ready = false;
     };
     hipStream_t _stream;
     hipStreamCallback_t _callback;
     void* _userData;
-    std::mutex _mtx;
-    bool _ready;
 };