mtd: rawnand: arasan: Fix missing de-registration of NAND

The NAND chip-selects are registered for the Arasan driver during
initialization but are not de-registered when the driver is unloaded. As a
result, if the driver is loaded again, the chip-selects remain registered
and busy, making them unavailable for use.

Fixes: 197b88fe ("mtd: rawnand: arasan: Add new Arasan NAND controller")
Cc: stable@vger.kernel.org
Signed-off-by: Maciej Andrzejewski ICEYE <maciej.andrzejewski@m-works.net>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>