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>

Documentation/hwmon/f71882fg

@@ -14,6 +14,10 @@ Supported chips:
     Prefix: 'f71882fg'
     Addresses scanned: none, address read from Super I/O config space
     Datasheet: Available from the Fintek website
+  * Fintek F71889FG
+    Prefix: 'f71889fg'
+    Addresses scanned: none, address read from Super I/O config space
+    Datasheet: Should become available on the Fintek website soon
   * Fintek F8000
     Prefix: 'f8000'
     Addresses scanned: none, address read from Super I/O config space
@@ -51,6 +55,12 @@ supported. The right one to use depends on external circuitry on the
 motherboard, so the driver assumes that the BIOS set the method
 properly.
 
+Note that the lowest numbered temperature zone trip point corresponds to
+to the border between the highest and one but highest temperature zones, and
+vica versa. So the temperature zone trip points 1-4 (or 1-2) go from high temp
+to low temp! This is how things are implemented in the IC, and the driver
+mimicks this.
+
 There are 2 modes to specify the speed of the fan, PWM duty cycle (or DC
 voltage) mode, where 0-100% duty cycle (0-100% of 12V) is specified. And RPM
 mode where the actual RPM of the fan (as measured) is controlled and the speed