[media] V4L: add a new videobuf2 buffer state VB2_BUF_STATE_PREPARED

This patch prepares for a better separation of the buffer preparation
stage.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
2 files changed