As asked by @0xc0170 in PR #3934, we won't be using device_has for indicating RF/Crypto features any longer. RF config options moved to the SL_RAIL lib.json, crypto config options will come with mbedTLS integration.
Moving the per-board clock configuration (which oscillators are available on the board, their frequencies, and which ones to use) as config options to the target database. This way, they're more easily overridable when third parties start creating boards with EFM32 MCUs
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