Nokia RX-51: Make onenand working

set_gpmc_cs0() sets wrong timings and size for Nokia N900 onenand flash.
Fix that by setting the correct timings and size from the board code

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Tested-by: Pali Rohár <pali@kernel.org>