DVK peripheral switch control.

This example project uses the EFM32 CMSIS including DVK BSP (board
support package).

It sets up access to DVK registers, and toggles access/switches to 
various peripheral devices on the DVK. Each enabled DVK will have a 
corresponding orange LED lit up.

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