media: au0828: Fix green screen in analog

media: au0828: Fix green screen in analog

When the driver was converted to VB2 the original function to fix
green frame detection was removed and a default vb2 dqbuf function
was used instead. This vb2 dqbuf function leads to green frames not
being detected and correupting stream captures.

The vidioc_dqbuf function checks the greenscreen flag, and, if set
resets the stream to discard the green frame and decode a real frame.

Signed-off-by: Bradford Love <brad@nextdimension.cc>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>