hwmon: (k8temp) Fix temperature reporting for (most) K8 RevG CPUs

Current Temperature for K8 RevG desktop CPUs is a "normalized value"
which can be below ambient temperature.

As a consequence lots of RevG systems report temperatures like:

$ sensors
k8temp-pci-00c3
Adapter: PCI adapter
Core0 Temp:    +17 C
Core0 Temp:     +3 C
Core1 Temp:    +21 C
Core1 Temp:     +5 C

being quite below ambient temperature.
There are even reports of negative temperature values.

This patch corrects the temperature reporting of k8temp for
RevG desktop CPUs.

Cc: Rudolf Marek <r.marek@assembler.cz>
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>