Timing helper can be used to profile code execution from user space.
Cache invalidation is organized in tasklet and will be removed from mem
driver after some testing is performed.

WIP: hw pointer offset error is still there

It looks like compessor is reporting erroneous HW pointer when last
frame ends precisely at the end of buffer and 32 zero bytes start from
the beginning of the buffer. HW pointer in this case should be 0x20, but
it is 0x00 in fact. This situation is detected and fixed in updateIRQJPEG_wp.

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.