mtd: nand: denali: squash setup_ecc_for_xfer() helper into caller

The setup_ecc_for_xfer() is only called from denali_data_xfer().
This helper is small enough, so squash it into the caller.
This looks cleaner to me.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>