hwmon: (nct6775) Add support for pwm, pwm_mode, and pwm_enable

Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/nct6775

@@ -69,6 +69,24 @@ is driven slower/faster to reach the predefined range again.
 
 The mode works for fan1-fan5.
 
+sysfs attributes
+----------------
+
+pwm[1-5] - this file stores PWM duty cycle or DC value (fan speed) in range:
+	   0 (lowest speed) to 255 (full)
+
+pwm[1-5]_enable - this file controls mode of fan/temperature control:
+	* 0 Fan control disabled (fans set to maximum speed)
+	* 1 Manual mode, write to pwm[0-5] any value 0-255
+	* 2 "Thermal Cruise" mode
+	* 3 "Fan Speed Cruise" mode
+	* 4 "Smart Fan III" mode (NCT6775F only)
+	* 5 "Smart Fan IV" mode
+
+pwm[1-5]_mode - controls if output is PWM or DC level
+        * 0 DC output
+        * 1 PWM output
+
 Usage Notes
 -----------