In VID mode, output voltages are measured and reported as VID values, and
have to be converted to voltages using VID conversion tables or functions.
Support is added for VR11 only at this time.

This patch enables support for PMBus devices supporting VID VR11 based output
voltage selection such as NCP4200 and NCP4208.
Signed-off-by: NGuenter Roeck <guenter.roeck@ericsson.com>
Reviewed-by: NRobert Coulson <robert.coulson@ericsson.com>