media: imx: TODO: Remove media link creation todos

  decided whether this feature is useful enough to make it generally

  available by exporting to v4l2-core.

- After all async subdevices have been bound, v4l2_fwnode_parse_link()

  is used to form the media links between the devices discovered in

  the OF graph.

  While this approach allows support for arbitrary OF graphs, there

  are some assumptions for this to work:

  1. If a port owned by a device in the graph has endpoint nodes, the

     port is treated as a media pad.

     This presents problems for devices that don't make this port = pad

     assumption. Examples are SMIAPP compatible cameras which define only

     a single output port node, but which define multiple pads owned

     by multiple subdevices (pixel-array, binner, scaler). Or video

     decoders (entity function MEDIA_ENT_F_ATV_DECODER), which also define

     only a single output port node, but define multiple pads for video,

     VBI, and audio out.

     A workaround at present is to set the port reg properties to

     correspond to the media pad index that the port represents. A

     possible long-term solution is to implement a subdev API that

     maps a port id to a media pad index.

  2. Every endpoint of a port owned by a device in the graph is treated

     as a media link.

     Which means a port must not contain mixed-use endpoints, they

     must all refer to media links between V4L2 subdevices.

- i.MX7: all of the above, since it uses the imx media core

- i.MX7: use Frame Interval Monitor