Reduce foot print of cycle1 -> cycle2 dma size change for fast adcs.

Old code for changing DMA size from the ( possibly smaller ) first cycle was too expensive in some sense, causing momentary channel hopping on the ADC when run at 65k and time_shift=0.

The new code just changes the size value of an already existing DMA module instead of totally recreating it.

assigned to @ezekiel.dohmen

approved this merge request

merged

mentioned in commit bf30af07