media: ti-vpe: cal: Hardcode virtual channel to 0

Using the endpoint reg value to pass the CSI-2 source virtual channel ID
in DT is a hack, isn't documented in the DT bindings, and isn't used in
neither upstream DT nor TI official overlays. Hardcode the virtual
channel to 0 to simplify reworking the code, proper virtual channel
support will be implemented later.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>