media: staging/imx: Switch to sync registration for IPU subdevs

media: staging/imx: Switch to sync registration for IPU subdevs

Because the IPU sub-devices VDIC and IC are not present in the
device-tree, platform devices were created for them instead. This
allowed these sub-devices to be added to the media device's async
notifier and registered asynchronously along with the other
sub-devices that do have a device-tree presence (CSI and devices
external to the IPU and SoC).

But that approach isn't really necessary. The IPU sub-devices don't
actually require a backing device (sd->dev is allowed to be NULL).
And that approach can't get around the fact that the IPU sub-devices
are not part of a device hierarchy, which makes it awkward to retrieve
the parent IPU of these devices.

By registering them synchronously, they can be registered from the CSI
async bound notifier, so the init function for them can be given the CSI
subdev, who's dev->parent is the IPU. That is a somewhat cleaner way
to retrieve the parent IPU.

So convert to synchronous registration for the VDIC and IC task
sub-devices, at the time a CSI sub-device is bound. There is no longer
a backing device for them (sd->dev is NULL), but that's ok. Also
set the VDIC/IC sub-device owner as the IPU, so that a reference can
be taken on the IPU module.

Since the VDIC and IC task drivers are no longer platform drivers,
they are now statically linked to imx-media module.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>