nand: davinci: add support for 4K page size nand devices

It is needed for k2l keystone2 EVM which uses NAND flash with 4K page
size, hence add support for 4K page size nand devices.

[Brian: similar work submitted by Murali Karicheri <m-karicheri2@ti.com>
and Hao Zhang <hzhang@ti.com>]

Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>