Merge pull request #3080 from citra-emu/Subv-ReleaseMutex-Return

Kernel/Mutex: Add a missing return in Mutex::Release

src/core/hle/kernel/mutex.cpp

@@ -88,6 +88,8 @@ ResultCode Mutex::Release(Thread* thread) {
         WakeupAllWaitingThreads();
         Core::System::GetInstance().PrepareReschedule();
     }
+
+    return RESULT_SUCCESS;
 }
 
 void Mutex::AddWaitingThread(SharedPtr<Thread> thread) {