mtd: rawnand: mtk: Fix init error path

Reviewing a series converting the for_each_chil_of_node() loops into
their _scoped variants made me realize there was no cleanup of the
already registered NAND devices upon error which may leak memory on
systems with more than a chip when this error occurs. We should call the
_nand_chips_cleanup() function when this happens.

Fixes: 1d6b1e46 ("mtd: mediatek: driver for MTK Smart Device")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Matthias Brugger <matthias.bgg@kernel.org>
Link: https://lore.kernel.org/linux-mtd/20240826153019.67106-2-miquel.raynal@bootlin.com