ARM: LPC32xx: Update DTS file for EA3250 board

This DTS file update adds:
* 3-channel ADC (for AD-IN on AD2, or 3-axis-accelerometer)
* Interrupt key

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