[media] tvp5150: use sd internal ops .registered instead .registered_async

The driver is using the struct v4l2_subdev_core_ops .registered_async
callback to register the connector entities and create the pad links
after the subdev entity has been registered with the media device.

But the .registered_async callback isn't needed since the v4l2 core
already calls the struct v4l2_subdev_internal_ops .registered callback
in v4l2_device_register_subdev(), after media_device_register_entity().

So, use the .registered() callback instead of the .registered_async()
that is going to be removed in a following patch since isn't needed.

Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>