media: coda: add min number of buffers controls

Add min number of buffers for capture (decoder) and output (encoder)
controls, which are required by the stateful video decoder / encoder
interface specification.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>