Input: twl6040-vibra - do not reparent to grandparent

For devm-managed input devices we should not modify input device's parent,
otherwise automatic release of resources will not work properly.

Tested-by: "H. Nikolaus Schaller" <hns@goldelico.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>