mtd: nand: davinci: return ENOMEM if memory allocation is failed

In case when memory allocation is failed the driver should return
ENOMEM instead of ENODEV.

Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Taras Kondratiuk <taras@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>