mtd: nand: use NAND_HAS_CACHEPROG

We have this unused macro, let's use it and justify its existence.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>