mtd: rawnand: omap_gpmc: fix OF based partition parsing for NAND

Set NAND chip ofnode and device so OF based partition parsing
can work.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Link: https://www.mail-archive.com/u-boot@lists.denx.de/msg499178.html


Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>