[media] v4l: vsp1: Release buffers at stream stop

videobuf2 expects no buffer to be owned by the driver when the
stop_stream queue operation returns. As the vsp1 driver fails to do so,
a warning is generated at stream top time.

Fix this by releasing all buffers queued on the IRQ queue in the
stop_stream operation handler and marking them as erroneous.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>