Before using block_isbad() check if mtd->block_isbad() is defined.
Calculating pgcnt must be done using pgsize defined to 512 on
NOR and mtd->writesize for NAND, not using  mtd->writesize directly.
Signed-off-by: NMorten Thunberg Svendsen <mts.doredevelopment@gmail.com>
Acked-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>