arm64: dts: freescale: sl28: enable fan support

Add a pwm-fan mapped to the PWM channel 0 which is connected to the
fan connector of the carrier.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts

@@ -15,6 +15,15 @@ / {
 	compatible = "kontron,sl28-var3-ads2", "kontron,sl28-var3",
 		     "kontron,sl28", "fsl,ls1028a";
 
+	pwm-fan {
+		compatible = "pwm-fan";
+		cooling-min-state = <0>;
+		cooling-max-state = <3>;
+		#cooling-cells = <2>;
+		pwms = <&sl28cpld_pwm0 0 4000000>;
+		cooling-levels = <1 128 192 255>;
+	};
+
 	sound {
 		#address-cells = <1>;
 		#size-cells = <0>;