media: uapi: move H264 stateless controls out of staging

The H.264 stateless 'uAPI' was staging and marked explicitly in the
V4L2 specification that it will change and is unstable.

Note that these control IDs were never exported as a public API,
they were only defined in kernel-local headers (h264-ctrls.h).

Now, the H264 stateless controls is ready to be part
of the stable uAPI.

While not too late, let's rename them and re-number their
control IDs, moving them to the newly created stateless
control class, and updating all the drivers accordingly.

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>