media: ti-vpe: cal: change index and cport to u8

cal_ctx's index and cport fields are numbers less than 8. In the
following patches we will get a bunch of new fields, all of which are
similar small numbers, so lets change the type to u8.

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