hwmon: (it87) Report thermal sensor type as Intel PECI if appropriate

IT8721 and IT8728 support Intel PECI temperature reporting. Each sensor
can be programmed to display the temperature reported on the PECI interface.

If configured for Intel PECI, the driver reported the wrong sensor type for
the respective thermal sensor. Fix the code to correctly report it as
"Intel PECI (6)".

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>