media: cedrus: Adjust buffer size based on codec

In some cases decoding engine needs extra space in capture buffers. This
is the case for decoding 10-bit HEVC frames into 8-bit capture format.
This commit only adds infrastructure for such cases.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>