The V4L2_CID_JPEG_CLASS control class is intended to expose various
adjustable parameters of JPEG encoders and decoders. Following controls
are defined:

 - V4L2_CID_JPEG_CHROMA_SUBSAMPLING,
 - V4L2_CID_JPEG_RESTART_INTERVAL,
 - V4L2_CID_JPEG_COMPRESSION_QUALITY,
 - V4L2_CID_JPEG_ACTIVE_MARKER.

This covers only a part of relevant standard specifications. More
controls should be added in future if required.

The purpose of V4L2_CID_JPEG_CLASS class is also to replace some
functionality covered by VIDIOC_S/G_JPEGCOMP ioctls, i.e. the JPEG
markers presence and compression quality control. The applications
and drivers should switch from the ioctl to control based API, as
described in the subsequent patches for the Media API DocBook.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>