ARM: dts: rockchip: fix pwm-cells for rk3288's pwm3

This is the same as the other PWMs on this SoC and uses 3 cells.
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288.dtsi

@@ -710,7 +710,7 @@ pwm2: pwm@ff680020 {
 	pwm3: pwm@ff680030 {
 		compatible = "rockchip,rk3288-pwm";
 		reg = <0x0 0xff680030 0x0 0x10>;
-		#pwm-cells = <2>;
+		#pwm-cells = <3>;
 		pinctrl-names = "default";
 		pinctrl-0 = <&pwm3_pin>;
 		clocks = <&cru PCLK_RKPWM>;