mtd: rawnand: nandsim: Stop using nand_release()

nand_release() basically calls mtd_device_unregister() and
nand_cleanup(). Both helpers should be called after MTD device
registration and NAND scan, respectively. Drop nand_release() and use
the two helpers directly so that they fit the error path and the
labels there.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200525085851.17682-12-miquel.raynal@bootlin.com