Prepare to divide videobuf2
- Separate vb2 trace events from v4l2 trace event.
- Make wrapper functions that will move to v4l2-side.
- Make vb2_core_* functions that will remain in core-side.
- Add a callback function table for buffer operation which makes vb2-core
  to be able to invoke a v4l2-side functions.
- Rename internal functions as vb2_*.
Signed-off-by: NJunghak Sung <jh1009.sung@samsung.com>
Signed-off-by: NGeunyoung Kim <nenggun.kim@samsung.com>
Acked-by: NSeung-Woo Kim <sw0312.kim@samsung.com>
Acked-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>