Scheduler: Add protections for Yield bombing

In case of redundant yields, the scheduler will now idle the core for 
it's timeslice, in order to avoid continuously yielding the same thing 
over and over.

src/core/hle/kernel/thread.h

@@ -408,13 +408,13 @@ public:
     void Sleep(s64 nanoseconds);
 
     /// Yields this thread without rebalancing loads.
-    void YieldSimple();
+    bool YieldSimple();
 
     /// Yields this thread and does a load rebalancing.
-    void YieldAndBalanceLoad();
+    bool YieldAndBalanceLoad();
 
     /// Yields this thread and if the core is left idle, loads are rebalanced
-    void YieldAndWaitForLoadBalancing();
+    bool YieldAndWaitForLoadBalancing();
 
     ThreadSchedStatus GetSchedulingStatus() const {
         return static_cast<ThreadSchedStatus>(scheduling_state & ThreadSchedMasks::LowMask);