Fix NAND FLASH timings for at91sam9x evaluation kits.

New timings are based on application note
"NAND Flash Support on AT91SAM9 Microcontrollers" available at
http://atmel.com/dyn/resources/prod_documents/doc6255.pdfSigned-off-by: NPatrice Vilchez <patice.vilchez@atmel.com>
Signed-off-by: NJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: NStelian Pop <stelian@popies.net>