mtd: rawnand: toshiba: Pass a single nand_chip object to the status helper

Now that most of the raw NAND API is consistent and has almost all its
helpers and hooks using a single nand_chip object instead of an mtd_info
one (or both), let's do the same cleanup in the raw NAND vendors
drivers.

Apply this change to the Toshiba driver so that the internal helper to
retrieve the ECC status does only take a nand_chip object.

Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>