media: ti-vpe: cal: Decouple CSI2 port and CPORT

The CPORT mentioned in the CAL documentation has nothing to do with the
CSI-2 ports. It's a remnant of CSI-3 support (or an attempt to achieve
it), and now only serves as an arbitraty tag value used to associate
data samples with contexts. Add a cport field to the cal_ctx structure
and use it instead of the CSI-2 port number where a CPORT is required by
the hardware. The value of the cport field is currently the same as the
csi2_port field, so there's no functional change, but this will help
reworking CPORT and CSI-2 port handling separately.

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>