ARM: imx27: add missing #pwm-cells property

The pwm-node is missing its #pwm-cells property. The pwm-framework will
complain about this.

Add the missing property.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx27.dtsi

@@ -123,6 +123,7 @@
 			};
 
 			pwm: pwm@10006000 {
+				#pwm-cells = <2>;
 				compatible = "fsl,imx27-pwm";
 				reg = <0x10006000 0x1000>;
 				interrupts = <23>;