Potentiometer control example.

This example project uses the EFM32 CMSIS including DVK BSP (board
support package) and demonstrates the use of the ADC/potentiometer in 
polled mode.

The user LEDs are used to indicate the setting of the potentiometer.

Board:  Silicon Labs EFM32-Gxxx-DK Development Kit
Device: EFM32G290F128 and EFM32G890F128
