Fifo: Extract syncing loop

It's now a new helper function within common.

Source/Core/Core/CoreTiming.cpp

@@ -475,7 +475,7 @@ void Idle()
 {
 	//DEBUG_LOG(POWERPC, "Idle");
 
-	if (SConfig::GetInstance().m_LocalCoreStartupParameter.bSyncGPUOnSkipIdleHack)
+	if (SConfig::GetInstance().m_LocalCoreStartupParameter.bSyncGPUOnSkipIdleHack && !SConfig::GetInstance().m_LocalCoreStartupParameter.bSyncGPU)
 	{
 		//When the FIFO is processing data we must not advance because in this way
 		//the VI will be desynchronized. So, We are waiting until the FIFO finish and