mtd: rawnand: Pass a nand_chip object to chip->erase()

Let's make the raw NAND API consistent by patching all helpers and
hooks to take a nand_chip object instead of an mtd_info one or
remove the mtd_info object when both are passed.

Let's tackle the chip->erase() hook.

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