arm: dts: mt2701: Add nand device node

Add mt2701 nand device node, include nfi and bch ecc.

Signed-off-by: Xiaolei Li <xiaolei.li@mediatek.com>
Signed-off-by: Erin Lo <erin.lo@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>