XTAL frequency detection, support for selecting XTAL frequency
This MR adds more robust XTAL frequency detection code (which gets run in the bootloader) and an option to set XTAL frequency in Kconfig. By default we still use autodetection, since it is more reliable than the one used in ROM code.
This will help with issues about XTAL frequency detection in high ambient temperature conditions.
Ref TW12008
See merge request !694