v4l2object: mark jpeg as parsed
Assuming that V4L2 CAPTURE devices always use one buffer per JPEG image, we can always mark JPEGs provided by a V4L2 element as parsed.
The V4L2 elements require that JPEG images sent to V4L2 OUTPUT devices must always be parsed.
This is necessary to link a V4L2 CAPTURE device with a V4L2 OUTPUT device without explicitly marking the stream as parsed or adding a jpegparse into the pipeline.