Since commit 
648cd48c9e566f53c5df30d79857e0937ae13b09
The hwmon name attributes must not include '-' so the name must be
rename from gpio-fan to gpio_fan
Signed-off-by: Julien D'Ascenzio <jdascenzio@yahoo.fr>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
 
        /* Make this driver part of hwmon class. */
        fan_data->hwmon_dev = hwmon_device_register_with_groups(&pdev->dev,
-                                               "gpio-fan", fan_data,
+                                               "gpio_fan", fan_data,
                                                gpio_fan_groups);
        if (IS_ERR(fan_data->hwmon_dev))
                return PTR_ERR(fan_data->hwmon_dev);