Mutex: Add the calling thread to the waiting list when needed

This will happen when the mutex is already owned by another thread. Should fix some issues with games being stuck due to waiting threads not being awoken.

src/core/hle/kernel/mutex.cpp

@@ -168,9 +168,9 @@ Handle CreateMutex(bool initial_locked, const std::string& name) {
 ResultVal<bool> Mutex::WaitSynchronization() {
     bool wait = locked;
     if (locked) {
+        waiting_threads.push_back(GetCurrentThreadHandle());
         Kernel::WaitCurrentThread(WAITTYPE_MUTEX, GetHandle());
-    }
-    else {
+    } else {
         // Lock the mutex when the first thread accesses it
         locked = true;
         MutexAcquireLock(this);