STM32: Review of last STM32 F2 PR. Progate changes to STM32 F4 and F7 OTGHS. ...

STM32: Review of last STM32 F2 PR.  Progate changes to STM32 F4 and F7 OTGHS.  Rename some configs/photon/src files.  Naming can be either photon_ or stm32_ but must be consistent.