media: i2c: vgxy61: Report stream using frame descriptors

Add support for .get_frame_desc() to report CSI-2 virtual channel
and data type information. This allows CSI-2 receivers to properly
interpret the stream without inferring the data type from the pixel
format.

Signed-off-by: Julien Massot <julien.massot@collabora.com>
Reviewed-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>