da850evm: setup the NAND flash timings

The default NAND flash timings are very conservative. This patch assigns the
timings reccomended in the recent linux kernel patch [1] from Sekhar Nori. The
speedup, as reported in that patch, is 5.3x for reads.

[1] http://www.spinics.net/lists/arm-kernel/msg100278.html



Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
CC: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>