mtd: nand: denali: call nand_set_flash_node() to set DT node

This will allow nand_dt_init() to parse DT properties in the NAND
controller device node.

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