Added component containg API that is able to correct raw ADC readings
into a voltage in mV. Also provided a helper function that combines
the process of getting the raw ADC1 reading then converting it to a
voltage in mV. In doing so, the adc1_get_voltage() function of the ADC
driver has been deprecated. Instead there is now adc1_get_raw to obtain
the raw ADC1 reading, and adc1_to_voltage() that gets the raw reading
and converts all in one function. Functions using the deprecated
adc1_get_voltage() have also been updated to use adc1_get_raw().
Conversion is based on ADC characteristics. The characteristics are based
on the ADC's v_ref, herefore the appropriate structure and functions have
been provided to obtain the ADC characteristics.
The existing ADC driver has also been modified by adding a function to
route the internal ADC reference voltage to a GPIO allowing users to measure
it manually.
Relevant documentation has also been updated
