ControllerInterface: Make UpdateInput / UpdateOutput return void

The return values here have never been checked, so it doesn't make sense
to return a value to begin with.

Source/Core/InputCommon/ControllerInterface/Xlib/Xlib.h

@@ -70,7 +70,7 @@ private:
 	};
 
 public:
-	bool UpdateInput() override;
+	void UpdateInput() override;
 
 	KeyboardMouse(Window window);
 	~KeyboardMouse();