mtd: rawnand: oxnas: Unregister all devices on error

commit b60391eb upstream.

On error, the oxnas probe path just frees the device which failed and
aborts the probe, leaving unreleased resources.

Fix this situation by calling mtd_device_unregister()/nand_cleanup()
on these.

Fixes: 66859249 ("mtd: nand: Add OX820 NAND Support")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200519130035.1883-38-miquel.raynal@bootlin.com


Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>