AV1 hardware decoder needs entropy parameters to decode frames.
They are computed from various arrays defined in AV1 section
"9.4. Default CDF tables".

Add helpers functions to init, store and get these parameters.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>