mtd: rawnand: denali: use helper function for ecc setup

Use the NAND core helper function nand_ecc_choose_conf to tune
the ECC parameters instead of the function locally defined.

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>