mtd: spinand: Delay a little bit the dirmap creation

As we will soon tweak the dirmap creation to act a little bit
differently depending on the picked ECC engine, we need to initialize
dirmaps after ECC engines. This should not have any effect as dirmaps
are not yet used at this point.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20220127091808.1043392-8-miquel.raynal@bootlin.com