media: controls: Add the stateless codec control class

Add a new control class to hold the stateless codecs controls
that are ready to be moved out of staging.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Tested-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>