* Cleanup Makefiles
Given the targets are now simply the MCU, there is now a significant amount of duplication.
TODO:
- will possibly add STM32.mk for inclusion from STM32F4 etc to remove further duplication.
Noting it is now imperative that the gating is right.
* Removed the remnants of "features"
* Further clean up in preparation of new MCUs
* Typo for STM32F722xx
* Fix F411
* Last remnants of the _TARGETS lists.