mtd: nand: vf610: remove the unnecessary of_node_put()

Calling of_node_put() in vf610_nfc_probe() is wrong because nothing in
this code retains a reference to the DT node.

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>