Input: twl6040-vibra - fix DT node memory management

commit e7ec014a

 ("Input: twl6040-vibra - update for device tree support")

made the separate vibra DT node to a subnode of the twl6040.

It now calls of_find_node_by_name() to locate the "vibra" subnode.
This function has a side effect to call of_node_put on() for the twl6040
parent node passed in as a parameter. This causes trouble later on.

Solution: we must call of_node_get() before of_find_node_by_name()

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