mtd: nand: set the cell information for ONFI nand

The current code does not set the SLC/MLC information for onfi nand.
(This makes that the kernel treats all the onfi nand as SLC nand.)

This patch fills the cell information for ONFI nands.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>