Now that we have targets.json, we get target inheritance and can use it to clean up the EFM32 folder structure.
* In the top-level EFM32 folder, there are now folders per MCU family (Giant, Leopard, ...)
* Those family folders contain the CMSIS headers in the 'device' subfolder, as well as global family headers (i.e. mapping of pins to peripherals)
* Inside of the family folder, there is a per-target folder containing target settings. In the future, we'll want to get rid of those by using the config system provided by targets.json
First wave of squashing header files in order to get to a more sensible folder tree.
* Moved header files with 100% similarity to common folder
* Created a CommonPinNames.h header containing the base pin names P[A-F][0-15] and NC
Steven Cooreman
Alessandro Angelino
Christopher Haster