mtd: nand: mtk: disable ecc irq when writing page with hwecc

Currently, ecc encode irq is enabled when writing page with hwecc, but
we actually do not wait for this irq done. Because NFI and ECC work in
parallel, nfi irq and ecc irq almost come together.

Now, there are two steps to check whether page data are totally written.
First, wait for nfi irq INTR_AHB_DONE. This is to ensure all data
in RAM are received by NFI.
Second, polling the register NFI_ADDRCNTR till all data include ecc
parity data runtime generated by ECC are sent to NAND device.

So, it is redunant to enable ecc irq without waiting for it.

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