mtd: onenand: add support for chips with 4KiB page size

This patch adds support for OneNAND chips that have 4KiB page size.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>