arm64: dts: rockchip: Add PWM fan for RockPro64

RockPro64 has a dedicated circuit for driving a 12V fan from PWM1.

At the moment this makes fan spin at full speed. fancontrol can be used
to control fan speed. E.g. the following config file works well:

INTERVAL=10
DEVPATH=hwmon0=devices/platform/pwm-fan
DEVNAME=hwmon0=pwmfan
FCTEMPS=hwmon0/device/pwm1=../thermal/thermal_zone0/temp
MINTEMP=hwmon0/device/pwm1=40
MAXTEMP=hwmon0/device/pwm1=60
MINSTART=hwmon0/device/pwm1=100
MINSTOP=hwmon0/device/pwm1=70

In the future it would be nice to define trip points in dts file,
so that kernel could adjust fan speed itself.
Signed-off-by: Andrius Štikonas <andrius@stikonas.eu>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-rockpro64.dts

@@ -58,6 +58,13 @@ diy-led {
 		};
 	};
 
+	fan: pwm-fan {
+		compatible = "pwm-fan";
+		#cooling-cells = <2>;
+		fan-supply = <&vcc12v_dcin>;
+		pwms = <&pwm1 0 50000 0>;
+	};
+
 	sdio_pwrseq: sdio-pwrseq {
 		compatible = "mmc-pwrseq-simple";
 		clocks = <&rk808 1>;
@@ -602,6 +609,10 @@ &pwm0 {
 	status = "okay";
 };
 
+&pwm1 {
+	status = "okay";
+};
+
 &pwm2 {
 	status = "okay";
 };