hwmon: (gpio-fan) move fan_alarm_init after devm_hwmon_device_register_with_groups

This makes it possible to use the hwmon_dev in fan_alarm_notify(). Otherwise
it would be possible, that a interupt arrives and fan_alarm_notify() is
executed, before hwmon_dev is initialized.

Signed-off-by: Christian Schneider <cschneider@radiodata.biz>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>