mtd: vf610_nfc: add 32-error correction option for HW ECC

Add option to choose between current 24-error correction and 32-error
correction through Kconfig. 32-error correction allow to use NAND
chips which require up to 8-bit error correction per 512 byte (when
using 2K pages).

Signed-off-by: Stefan Agner <stefan@agner.ch>