[ARM] at91: 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.pdf).

Signed-off-by: Patrice Vilchez <patrice.vilchez@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>