media: imx: Move pads init to probe

If a subdevice is unregistered and then registered again without the
driver being removed and re-probed (which will happen when the media
device is removed and re-probed without also removing/re-probing the
subdevice), media_device_register_entity() is called with a non-zero
entity->num_pads, and then the subdevice's .registered callback calls
media_entity_pads_init(). Thus the subdevice's pad objects are added
to the media device pad list twice, causing list corruption.

One way to fix this would be to create media_entity_pads_destroy(),
and call it in the subdevice's .unregistered callback. But calling
media_entity_pads_init() in the .registered callbacks was done for
legacy reasons and is no longer necessary, so move the call to
media_entity_pads_init() into the subdevice's probe functions. This
fixes the duplicate pad obejcts in the media device pad list.

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>