media: ti-vpe: cal: Add CSI2 context

CAL has 8 CSI2 contexts per PHY, which are used to tag the incoming
data.  The current driver only uses the first context, but we need to
support all of them to implement multi-stream support.

Add a csi2_ctx field to cal_ctx, which indicates which of the 8 CSI2
contexts is used for the particular cal_ctx. Also clean up the context
register macros to take the CSI2 context number as a parameter.

Note that before this patch the CSI2 context used for both PHYs was
always 0. This patch always uses cal_ctx index number as the CSI2
context. There is no functional difference, but this approach will work
also in the future when we use more than 1 CSI2 context per PHY.

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>