STM32 DMAv3 driver.

Driver capability:

- The driver supports the STM32 enhanced DMA controller found on H7 sub-family.
- Support for cache flushing and invalidation.

The file registry must export:

STM32_HAS_DMAx              - Support for DMA unit "x" (1..2).
STM32_DMAx_CHn_HANDLER      - Vector name for channel "n" (0..7).
STM32_DMAx_CHn_NUMBER       - Vector number for channel "n" (0..7).