[stm32f7] Add support for stm32f7 microcontrollers
Updated features:
- SD card driver
- Backup domain driver (old Safe-Guard-Memory)
- 767 Nucleo, 769 Discovery and Skyward's Compute Unit boards support
- Added
V_DDA_VOLTAGE
macro on most boards to specify the analog supply voltage - Fixed wrong sd card voltages on some Skyward's boards