The FWHT stateless 'uAPI' was staging and marked explicitly in the
V4L2 specification that it will change and is unstable.
Note that these control IDs were never exported as a public API,
they were only defined in kernel-local headers (fwht-ctrls.h).

Now, the FWHT stateless controls is ready to be part
of the stable uAPI.

While not too late:

- Rename V4L2_CID_MPEG_VIDEO_FWHT_PARAMS to V4L2_CID_STATELESS_FWHT_PARAMS.

- Move the contents of fwht-ctrls.h to v4l2-controls.h.

- Move the public parts of drivers/media/test-drivers/vicodec/codec-fwht.h
  to v4l2-controls.h.

- Add V4L2_CTRL_TYPE_FWHT_PARAMS control initialization and validation.

- Add p_fwht_params to struct v4l2_ext_control.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>