mtd: nand: davinci: add support for on-die ECC engine type

Some chips, e.g. Micron MT29F1G08ABBFAH4, has a mandatory on-die ECC.
Add "on-die" as ECC engine type in order to be compatible with those.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>