mtd: MLC device check in OneNAND driver

The MLC NAND Flash differs from the SLC NAND flash in functioning
and the cell structure. Therefore we are considering it as a
different Flash type.

Signed-off-by: Rohit H.S <rohit.hs@samsung.com>
Signed-off-by: Raghav Gupta <gupta.raghav@samsung.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>