hwmon: (w83795) Exclude fan control feature by default

The fan control feature of the w83795 driver is insufficiently
reviewed and tested for public consumption at this time, so make it
optional and disabled by default. We will change the default when
review and testing is deemed sufficient. Ultimately the option will
go away.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>