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 <[e-mail]>
Reviewed-by: Andrzej Pietrasiewicz <[e-mail]>
CC: Antti Palosaari <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/usb/hackrf/hackrf.c

···
 		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);