media: vicodec: add V4L2_CID_MIN_BUFFERS_FOR_* controls

Stateful codecs must support the V4L2_CID_MIN_BUFFERS_FOR_OUTPUT
and V4L2_CID_MIN_BUFFERS_FOR_CAPTURE controls. The vicodec driver
was missing support for these controls. Add them.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>