ARM: dts: imx28-duckbill: use symbolic names from gpio.h

Use GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW instead of 0 and 1.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>