media: ti-vpe: cal: init ctx->v_fmt correctly in MC mode

CAL driver enumerates mbus codes in the connected subdev to create a
list of supported formats reported to userspace, and initializes
ctx->v_fmt and ctx->fmtinfo to one of those formats.

This works fine for legacy mode, but is not correct for MC mode, and the
list is not even used in MC mode.

Fix this by adding a new function, cal_ctx_v4l2_init_mc_format, which
only initializes ctx->v_fmt and ctx->fmtinfo to a default value.

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>