media: ti: cal: use frame desc to get vc and dt

Use get_frame_desc() to get the frame desc from the connected source,
and use the provided virtual channel and datatype instead of hardcoded
ones.

get_frame_desc() can contain multiple streams, but as we don't support
multiple streams yet, we will just always use the first stream.

If the source doesn't support get_frame_desc(), fall back to the
previous method of always capturing virtual channel 0 and any datatype.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>