ARM: dts: imx28-duckbill: fix phy reset gpio

Fix a copy & paste error: on duckbills the GPIO used for resetting
the ethernet phy differs from FSL's MX28EVK board.

Reported-by: Stefan Wahren <info@lategoodbye.de>
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>