hle: kernel: process: Add state lock.

src/core/hle/kernel/process.h

@@ -348,6 +348,10 @@ public:
     void PinCurrentThread();
     void UnpinCurrentThread();
 
+    KLightLock& GetStateLock() {
+        return state_lock;
+    }
+
     ///////////////////////////////////////////////////////////////////////////////////////////////
     // Thread-local storage management
 
@@ -472,6 +476,8 @@ private:
 
     KThread* exception_thread{};
 
+    KLightLock state_lock;
+
     /// System context
     Core::System& system;
 };