mtd: rawnand: oxnas: Fix the probe error path

nand_release() is supposed be called after MTD device registration.
Here, only nand_scan() happened, so use nand_cleanup() instead.

While at it, be consistent and move the function call in the error
path thanks to a goto statement.

Fixes: 66859249 ("mtd: nand: Add OX820 NAND Support")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-mtd/20200519130035.1883-37-miquel.raynal@bootlin.com