no board configure it as 'n' and it's an issue to merge all defconfigs
in one

On AT91SAM926x boards both types of NAND flash can be present
(8 and 16 bit data bus width).

so will pass it via system_rev
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Patrice Vilchez <patrice.vilchez@atmel.com>