media: uapi: mpeg2: Remove V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS

The Hantro and Cedrus drivers work in frame-mode,
meaning they expect all the slices in a picture (either frame
or field structure) to be passed in each OUTPUT buffer.

These two are the only V4L2 MPEG-2 stateless decoders currently
supported. Given the VA-API drivers also work per-frame,
coalescing all the MPEG-2 slices in a buffer before the decoding
operation, it makes sense to not expect slice-mode drivers and
therefore remove V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS.

This is done to avoid carrying an unused interface. If needed,
this control can be added without breaking backwards compatibility.
Note that this would mean introducing a enumerator control to
specify the decoding mode (see V4L2_CID_STATELESS_H264_DECODE_MODE).

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Co-developed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Tested-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>