ARM: dts: imx28: include gpio.h to allow use of symbolic names

Signed-off-by: NMichael Heimpold <mhei@heimpold.de>
Acked-by: NStefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: NShawn Guo <shawn.guo@freescale.com>

arch/arm/boot/dts/imx28.dtsi

@@ -9,6 +9,7 @@
  * http://www.gnu.org/copyleft/gpl.html
  */
 
+#include <dt-bindings/gpio/gpio.h>
 #include "skeleton.dtsi"
 #include "imx28-pinfunc.h"