hwmon: (i5500_temp) New driver for the Intel 5500/5520/X58 chipsets

The Intel 5500, 5520 and X58 chipsets embed a digital thermal sensor.
This new driver supports it.

Note that on many boards the sensor seems to be disabled and reports
the minimum value (36.5 degrees Celsius) all the time.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Romain Dolbeau <romain@dolbeau.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>