So far, the driver updates temp_auto_hyst and temp_auto_off if temp_auto_min changes.
This may cause problems if temp_auto_off was not configured before configuring
temp_auto_min, because one of the variables used (off_desired) is not initialized
in this case.

To simplify the code, and for consistency with other drivers, no longer update the delta
between "min" and "off" until the user sets the "off" value again.

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