STM32 DMA: replaced F4 header to match that for F2, and move header and source files to common.
In the header:
- Fix DMA_SxCR_CT: change shift from 18 to 19
For use with the convenience functions:
- Added DMA_SxCR_CHSEL generic values
- Added DMA_STREAM - generic values
- Added dma_if_offset - rather than separating out LISR and HISR
- Added masks
- Added dma_disable_double_buffer_mode()
Move STM32F1 DMA files to respective common directories
This sets the stage for adding DMA to STM32F3xx (when added) and STM32L1xx as the controller appears to be identical in these.