ARM: dts: imx6sx-nitrogen6sx: Use #pwm-cells = <3> for imx27-pwm device

The binding dictates using 3 pwm-cells. Adhere to that.

This fixes the following dtbs_check warning:

	arch/arm/boot/dts/nxp/imx/imx6sx-nitrogen6sx.dtb: pwm@208c000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#

There is no need for an explicit status = "okay" in the pwm node as
the soc dtsi doesn't disable this device. Drop this property, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: Uwe Kleine-König

arch/arm/boot/dts/nxp/imx/imx6sx-nitrogen6sx.dts

@@ -18,7 +18,7 @@
 
 	backlight-lvds {
 		compatible = "pwm-backlight";
-		pwms = <&pwm4 0 5000000>;
+		pwms = <&pwm4 0 5000000 0>;
 		brightness-levels = <0 4 8 16 32 64 128 255>;
 		default-brightness-level = <6>;
 		power-supply = <&reg_3p3v>;
@@ -229,10 +229,8 @@
 };
 
 &pwm4 {
-	#pwm-cells = <2>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_pwm4>;
-	status = "okay";
 };
 
 &ssi1 {