ARM: dts: imx25: Add #pwm-cells to pwm4

The property '#pwm-cells' is currently missing. It is not possible to
use pwm4 without this property.
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Fixes: 5658a68f ("ARM i.MX25: Add devicetree")
Cc: <stable@vger.kernel.org>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx25.dtsi

@@ -428,6 +428,7 @@ slcdc@53fc0000 {
 
 			pwm4: pwm@53fc8000 {
 				compatible = "fsl,imx25-pwm", "fsl,imx27-pwm";
+				#pwm-cells = <2>;
 				reg = <0x53fc8000 0x4000>;
 				clocks = <&clks 108>, <&clks 52>;
 				clock-names = "ipg", "per";