STM32 ADCv2 driver.

Driver capability:

- Supports the STM32 "advanced" ADC found on F2, F4 and F7 sub-families.

The file registry must export:

STM32_HAS_ADCx                  - ADCx presence flag (1..3).
STM32_ADC_HANDLER               - IRQ vector name for ADCs (shared).
STM32_ADC_NUMBER                - IRQ vector number for ADCs (shared).
STM32_ADCx_DMA_MSK              - Mask of the compatible DMA channels.
STM32_ADCx_DMA_CHN              - Mask of the channels mapping.