Some drivers are retrieving the nand_chip pointer using the container_of
macro on a struct wrapping both the nand_chip and the mtd_info struct while
the standard way of retrieving this pointer is through mtd->priv.
Provide an helper to do that.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: NBrian Norris <computersforpeace@gmail.com>