hwmon: (f71882fg) Add support for the f71889fg (version 2)

This adds support for the Fintek f71889fg to the f71882fg driver,
many thanks to Gerd v. Egidy for providing (remote) access to a
machine which such an ic.

Note that this bit of the patch:
-	val = SENSORS_LIMIT(val, 0, 255);
+
+	if (data->type == f71889fg)
+		val = SENSORS_LIMIT(val, -128, 127);
+	else
+		val = SENSORS_LIMIT(val, 0, 127);

Changes behaviour for already supported models, the new behaviour is correct
as the already supported models have bit 7 of the involved registers fixed at
0, so the previous behaviour which allowed setting temp zone limits > 127
was not correct.

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