mtd: rawnand: nandsim: Rename a label in ns_init_module()

Rename the "error" label to gave it a meaning.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200525085851.17682-17-miquel.raynal@bootlin.com