media: ti-vpe: cal: Replace number of ports numerical value by macro

Use the CAL_NUM_CSI2_PORTS macro instead of the hardcoded numerical
value 2 to iterate over the CSI-2 ports.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.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>