hwmon: (f71882fg) Cleanup fan and temp hyst functions

Simplify fan and temp hyst. handling by treating the registers as an array of
nibbles instead of using switch cases. Also unify the way hysts are handled
between temp and fans, the temp code was storing the actual per temp hyst
values in 4 u8's, where as the fan code was storing actual register values.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>