media: imx: capture: Rename ioctl operations with legacy prefix

The i.MX media drivers implement a legacy video node API, where the
format of the video node is influenced by the active format of the
connected subdev (both for enumeration and for the get, set and try
format ioctls), and where controls exposed by the subdevs in the
pipeline are inherited by the video node.

At the same time, the drivers implement the media controller API and
expose subdev video nodes to userspace. Those two modes of operation are
incompatible and should not be exposed together. Furthermore, the legacy
API gets in the way of proper enumeration of pixel formats on the video
node, as it prevents compliance with the V4L2 specification.

As a first step towards fixing this, rename all V4L2 video node ioctl
handlers with a legacy prefix. This will allow implementing a new set of
ioctls in parallel and gradually switching drivers. Add a task to the
TODO file for the removal of the legacy API.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/imx/TODO

@@ -17,9 +17,12 @@
 - This media driver supports inheriting V4L2 controls to the
   video capture devices, from the subdevices in the capture device's
   pipeline. The controls for each capture device are updated in the
-  link_notify callback when the pipeline is modified. It should be
-  decided whether this feature is useful enough to make it generally
-  available by exporting to v4l2-core.
+  link_notify callback when the pipeline is modified. This feature should be
+  removed, userspace should use the subdev-based userspace API instead.
+
+- Similarly to the legacy control handling, legacy format handling where
+  formats on the video nodes are influenced by the active format of the
+  connected subdev should be removed.
 
 - i.MX7: all of the above, since it uses the imx media core