evas: Fix use of invalid EO object

During a window destruction, the input devices are deleted and
removed from the internal devices list. Since 83d18617b4
basic devices are children of a seat, which means that the seat
deletion was triggering the devices deletion as well. As a
consequence, we were walking an invalid list of devices.

I'm not sure we should have a list of children in the device
data and I'm also not sure we should have a list of devices in
evas, instead of just the list of seats. It's a bit messy right
now.

Ref T5540

src/lib/evas/canvas/evas_device.c

@@ -207,6 +207,8 @@ evas_device_add_full(Evas *eo_e, const char *name, const char *desc,
           e->default_mouse = dev;
      }
 
+   // FIXME: All devices are in the same list, while evas only refs the seats
+   if (parent_dev) efl_ref(dev);
    e->devices = eina_list_append(e->devices, dev);
    efl_event_callback_add(dev, EFL_EVENT_DEL, _del_cb, e);