The following patch rewrites the temperature conversion macros and
functions found in the via686a chip driver. Contrary to the voltage
conversions a few weeks ago, temperature conversions were numerically
correct, but artificially complex. The new ones are cleaner. It also
fixes a highly improbable array overflow (would take one of the measured
temperatures to be over 145 degrees C).

Successfully tested by Mark D. Studebaker and I, and already applied to
our CVS repository.