spi: mtk-snfi: unregister ECC engine on probe failure and remove() callback

In the Linux kernel, the following vulnerability has been resolved: spi: mtk-snfi: unregister ECC engine on probe failure and remove() callback mtk_snand_probe() registers the on-host NAND ECC engine, but teardown was missing from both probe unwind and remove-time cleanup. Add a devm cleanup action after successful registration so nand_ecc_unregister_on_host_hw_engine() runs automatically on probe failures and during device removal.