mtd: spinand: Instantiate a SPI-NAND on-die ECC engine

Make use of the existing functions taken from the SPI-NAND core to
instantiate an on-die ECC engine specific to the SPI-NAND core. The
next step will be to tweak the core to use this object instead of
calling the helpers directly.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200930154109.3922-4-miquel.raynal@bootlin.com