[media] rcar-vin: decrease buffers needed to capture

It's possible to grab frames using only one buffer, this should never
have been set to anything else then 1.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/rcar-vin/rcar-dma.c

@@ -1183,7 +1183,7 @@ int rvin_dma_probe(struct rvin_dev *vin, int irq)
 	q->ops = &rvin_qops;
 	q->mem_ops = &vb2_dma_contig_memops;
 	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
-	q->min_buffers_needed = 2;
+	q->min_buffers_needed = 1;
 	q->dev = vin->dev;
 
 	ret = vb2_queue_init(q);