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

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

This fixes the following dtbs_check warnings:

	arch/arm/boot/dts/nxp/imx/imx6sx-sdb-reva.dtb: pwm@2088000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#
	arch/arm/boot/dts/nxp/imx/imx6sx-sdb-sai.dtb: pwm@2088000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#
	arch/arm/boot/dts/nxp/imx/imx6sx-sdb.dtb: pwm@2088000: #pwm-cells:0:0: 3 was expected
		from schema : http://devicetree.org/schemas/pwm/imx-pwm.yaml#
	arch/arm/boot/dts/nxp/imx/imx6sx-sdb-mqs.dtb: pwm@2088000: #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>

arch/arm/boot/dts/nxp/imx/imx6sx-sdb.dtsi

@@ -23,7 +23,7 @@ memory@80000000 {
 
 	backlight_display: backlight-display {
 		compatible = "pwm-backlight";
-		pwms = <&pwm3 0 5000000>;
+		pwms = <&pwm3 0 5000000 0>;
 		brightness-levels = <0 4 8 16 32 64 128 255>;
 		default-brightness-level = <6>;
 	};
@@ -295,10 +295,8 @@ display_out: endpoint {
 };
 
 &pwm3 {
-	#pwm-cells = <2>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_pwm3>;
-	status = "okay";
 };
 
 &snvs_poweroff {