Fully qualify enum arguments in input device manager signals

Otherwise queued connections may complain about DeviceType not being
registered.

Change-Id: I1f93f8b34e78919e72ea99000c42da7024b6bdf3
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/gui/kernel/qinputdevicemanager_p.h

@@ -79,7 +79,7 @@ public:
     void setCursorPos(const QPoint &pos);
 
 signals:
-    void deviceListChanged(DeviceType type);
+    void deviceListChanged(QInputDeviceManager::DeviceType type);
     void cursorPositionChangeRequested(const QPoint &pos);
 };