mtd: nand: mtk: use nand_reset() to reset NAND devices in resume function

Previously, we only select chips and then send reset command to a NAND
device during resuming nand driver. There is a lack of deselecting chips.
It is advised to reset and initialize a NAND device using nand_reset().

Signed-off-by: Xiaolei Li <xiaolei.li@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>