Never enable v4l2 buffer copies

If upstream element doesn't specify minimum amount of buffers in the
allocation query, e.g. 'tee', v4l2src enables buffer copying. Copying
of frames is super duper slow, way worse than pipelin stalls from too
few buffers. Never enable it.

Change-Id: Idda3598595ccbe38e3daa635789316f42cfa32e2
diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index c074196..5f09c2c 100755
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -4552,6 +4552,7 @@
      * frame. */
     own_min = min + obj->min_buffers + 2;
 
+#if 0
     /* If no allocation parameters where provided, allow for a little more
      * buffers and enable copy threshold */
     if (!update) {
@@ -4562,6 +4563,10 @@
       gst_v4l2_buffer_pool_copy_at_threshold (GST_V4L2_BUFFER_POOL (pool),
           FALSE);
     }
+#else
+    /* Never enable buffer copies as it significantly degrades performance. */
+    gst_v4l2_buffer_pool_copy_at_threshold (GST_V4L2_BUFFER_POOL (pool), FALSE);
+#endif
 
   } else {
     /* In this case we'll have to configure two buffer pool. For our buffer