hle: kernel: Recode implementation of KThread to be more accurate.

src/core/cpu_manager.cpp

@@ -279,8 +279,7 @@ void CpuManager::PreemptSingleCore(bool from_running_enviroment) {
     {
         auto& scheduler = system.Kernel().Scheduler(current_core);
         scheduler.Reload(scheduler.GetCurrentThread());
-        auto* currrent_thread2 = scheduler.GetCurrentThread();
-        if (!currrent_thread2->IsKernelThread()) {
+        if (!scheduler.IsIdle()) {
             idle_count = 0;
         }
     }