media: uvcvideo: refactor __uvc_ctrl_add_mapping

Pass the chain instead of the device. We want to keep the reference to
the chain that controls belong to.

We need to delay the initialization of the controls after the chains
have been initialized.

This is a cleanup needed for the next patches.

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>