ARM: dts: imx28-duckbill-2-enocean: Remove unnecessary #address/#size-cells

Remove unnecessary #address-cells/#size-cells to fix the following
DTC warnings:

arch/arm/boot/dts/imx28-duckbill-2-enocean.dtb: Warning (avoid_unnecessary_addr_size): /gpio-keys: unnecessary #address-cells/#size-cells without "ranges" or child "reg" propert

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>