ARM: LPC32xx: Add NAND flash timing to PHY3250 board dts

This patch adds necessary NAND flash timings to the board specific dts file of
the PHY3250 reference board of the LPC32xx SoC.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Tested-by: Alexandre Pereira da Silva <aletes.xgr@gmail.com>