mtd: rawnand: brcmnand: support v2.1-v2.2 controllers

v2.1: tested on Netgear DGND3700v1 (BCM6368)
v2.2: tested on Netgear DGND3700v2 (BCM6362)

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200522121524.4161539-6-noltari@gmail.com