media: atomisp: Remove custom VCM handling

Remove the custom VCM handling, instead the VCM should be controlled
through its own v4l2-subdev and the new ipu-bridge.c code already
supports instantiating an i2c_client for this and setting up
the necessary endpoints in the fwnode graph.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>