This commit adds DMA and TC support to SAMV7 AFEC driver. The AFEC (ADC)
can now be triggered by Timer/counter at chosen frewuency and samples can
be transfered via DMA with configurable number of samples. Timer/counter
trigger is now set as a default option with the possibility to change it
to software generated trigger.
DMA is inspired by SAMA5 driver and also uses ping pong buffers.
Signed-off-by: Michal Lenc <michallenc@seznam.cz>
ce53ea5da6