ARM i.MX53: mba53: Fix PWM backlight DT node

The i.MX53 PWM controller uses two cells to describe the PWM specifier.
Remove the extra unused values from the backlight DT node pwms property.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx53-mba53.dts

@@ -27,7 +27,7 @@ reg_backlight: fixed@0 {
 
 	backlight {
 		compatible = "pwm-backlight";
-		pwms = <&pwm2 0 50000 0 0>;
+		pwms = <&pwm2 0 50000>;
 		brightness-levels = <0 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96 100>;
 		default-brightness-level = <10>;
 		enable-gpios = <&gpio7 7 0>;