media: usb: hackrf: Stop direct calls to queue num_buffers field

Use vb2_get_num_buffers() to avoid using queue num_buffers field directly.
This allows us to change how the number of buffers is computed in the
future.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
CC: Antti Palosaari <crope@iki.fi>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/usb/hackrf/hackrf.c

@@ -753,12 +753,13 @@ static int hackrf_queue_setup(struct vb2_queue *vq,
 		unsigned int *nplanes, unsigned int sizes[], struct device *alloc_devs[])
 {
 	struct hackrf_dev *dev = vb2_get_drv_priv(vq);
+	unsigned int q_num_bufs = vb2_get_num_buffers(vq);
 
 	dev_dbg(dev->dev, "nbuffers=%d\n", *nbuffers);
 
 	/* Need at least 8 buffers */
-	if (vq->num_buffers + *nbuffers < 8)
-		*nbuffers = 8 - vq->num_buffers;
+	if (q_num_bufs + *nbuffers < 8)
+		*nbuffers = 8 - q_num_bufs;
 	*nplanes = 1;
 	sizes[0] = PAGE_ALIGN(dev->buffersize);