hwmon: (it87) Support PECI for additional chips

Extend support for reporting and selecting PECI temperature sensors
to IT8718, IT8720, IT8782, and IT8783. For IT8721, report the sensor
type for temp2 as Intel PECI (6) if the chip is configured to report
the PCH temperature.

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