Make single thread bench cheat-resistant

Each hash is dependent on the previous hash to make multi-threaded cheating impossible.

src/backend/opencl/OclBackend.cpp

@@ -463,7 +463,7 @@ void xmrig::OclBackend::start(IWorker *worker, bool ready)
     mutex.unlock();
 
     if (ready) {
-        worker->start();
+        worker->start(d_ptr->controller->config());
     }
 }
 

src/backend/opencl/OclWorker.cpp

@@ -163,7 +163,7 @@ size_t xmrig::OclWorker::intensity() const
 }
 
 
-void xmrig::OclWorker::start()
+void xmrig::OclWorker::start(xmrig::Config*)
 {
     cl_uint results[0x100];
 

src/backend/opencl/OclWorker.h

@@ -40,6 +40,7 @@ namespace xmrig {
 
 class IOclRunner;
 class Job;
+class Config;
 
 
 class OclWorker : public Worker
@@ -59,7 +60,7 @@ public:
 protected:
     bool selfTest() override;
     size_t intensity() const override;
-    void start() override;
+    void start(Config*) override;
 
 private:
     bool consumeJob();