Fix the NAND flash timings on the AT91SAM9260.

The current timings lead to the detection of a number of bad blocks.
These timings are now set the same as on the AT91SAM9263.

Patch from Nicolas Ferre.
Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>