media: hantro/cedrus: Remove unneeded slice size and slice offset
The MPEG2_SLICE_PARAMS control is designed to refer to a
single slice. However, the Hantro and Cedrus drivers operate
in per-frame mode, and so does the current Ffmpeg and GStreamer
implementations that are tested with these two drivers.
In other words, the drivers are expecting all the slices in a picture
(with either frame or field structure) to be contained in
the OUTPUT buffer, which means the slice size and offset shouldn't be used.