mtd: nand: denali: use nand_chip to hold frequently accessed data

The denali_init() needs to setup a bunch of parameters of nand_chip.
Replace denali->nand.(member) with chip->(member) for shorter code.

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