mtd: rawnand: Pass a nand_chip object to nand_scan()

Let's make the raw NAND API consistent by patching all helpers to take
a nand_chip object instead of an mtd_info one.

We start with nand_scan().

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