This commit should not compile and was made just to save current state.
framepars and sensor_common were converted to platform dirver, some file
headers were updated and ad-hoc updates to doxygen comments were
introduced.

circbuf driver was converted to platform driver, some unused lines of
code were commented out to delete them in the future. Currently the
driver is built in into kernel as I could not easily split it to
separate external modules due to various dependencies and issues during
linking stage.

This involves some modifications to meta-elphel layer.

dma_sync_sg_for_[cpu,device] were added. Driver crashes on reading large
block of data.