mtd: rawnand: vf610: Stop passing mtd_info to internal functions

Mimic what has been done in the core and avoid passing mtd_info object
internally.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>