ARM: dts: Update OMAP3430 SDP NAND and ONENAND properties

The GPMC timing properties for device-tree have been updated by adding
a "-ns" or "-ps" suffix to indicate the units of time the property
represents (as suggested by Rob Herring). Therefore, update the timing
property names for the OMAP3430 SDP NAND and ONENAND devices.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>