mtd: nand: arasan: Set ofnode value

Ofnode value is not set, so all the DT properties are not being read
and due to this default values are being used.

Find nand node and set chip->flash_node value.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Link: https://lore.kernel.org/r/20230224050709.30014-3-ashok.reddy.soma@amd.com


Signed-off-by: Michal Simek <michal.simek@amd.com>