hwmon: (pmbus) Add ADP4000, NCP4200 and NCP4208 to list of supported devices

Add ADP4000, NCP4200 and NCP4208 to the list of devices supported by the generic
PMBus driver, and add device IDs to enable explicit instantiation.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Reviewed-by: Robert Coulson <robert.coulson@ericsson.com>
Acked-by: Jean Delvare <khali@linux-fr.org>