mtd: nand: mediatek: add support for different MTK NAND FLASH Controller IP

ECC strength and spare size supported may be different among MTK NAND
FLASH Controller IPs.

This patch contains changes as following:
(1) add new struct mtk_nfc_caps to support different spare size.
(2) add new struct mtk_ecc_caps to support different ecc strength.
(3) remove ECC_CNFG_xBIT define, use a for loop to do ecc strength config.
(4) remove PAGEFMT_SPARE_ define, use a for loop to do spare format config.
(5) malloc ecc->eccdata buffer according to max ecc strength of this IP.

Signed-off-by: Xiaolei Li <xiaolei.li@mediatek.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>