V4L/DVB (6259): Fix vivi poll() method

Due to the replace of videobuf_read_one to videobuf_read_stream, poll()
method implementation is wrong. This fixes poll() implementation, making
read of /dev/video? to work again.

With this method, an USB driver can use video-buf, without needing to
request memory from the DMA-safe area.
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/vivi.c

@@ -1122,9 +1122,8 @@ vivi_poll(struct file *file, struct poll_table_struct *wait)
 	} else {
 		dprintk(1,"poll: read() interface\n");
 		/* read() capture */
-		buf = (struct vivi_buffer*)fh->vb_vidq.read_buf;
-		if (NULL == buf)
-			return POLLERR;
+		return videobuf_poll_stream(file, &fh->	vb_vidq,
+					    wait);
 	}
 	poll_wait(file, &buf->vb.done, wait);
 	if (buf->vb.state == STATE_DONE ||