vdiv - wrong output, misunderstanding of device function

[jontrulson]

• This driver is just wrong. It appears that someone didn't read the
  datasheet to understand what this device actually does. :)

• The 'scale' needs to be specified to init(). This has nothing to do
  with FTI scaling - rather there is an actual switch on the device
  that must be accounted for when computing voltage.

• And the output value should be an actual voltage, not a normalized ADC
  value (computedValue() in original CXX file). The whole purpose of
  the device is for measuring voltage :)

  Like others, this device does not average samples like it should.
  Needs fixing.

[pylbert]

Noted - will update to use the gain in the c src.