mtd: rawnand: brcmnand: fix hamming oob layout

First 2 bytes are used in large-page nand.

Fixes: ef5eeea6 ("mtd: nand: brcm: switch to mtd_ooblayout_ops")
Cc: stable@vger.kernel.org
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200512075733.745374-2-noltari@gmail.com