media: ti-vpe: cal: add vc and datatype fields to cal_ctx

In preparation for supporting multiple virtual channels and datatypes,
add vc and datatype fields to cal_ctx, initialize them to the currently
used values, and use those fields when writing to the register.

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>