v4l2src: fix for webcamstudio vloopback

Because vlooback emits 25 - ENOTTY and no EINVAL v4l2src thought it
can't handle this and does not work.

https://bugzilla.gnome.org/show_bug.cgi?id=669455

sys/v4l2/v4l2_calls.c

@@ -253,7 +253,7 @@ gst_v4l2_fill_lists (GstV4l2Object * v4l2object)
 
     control.id = n;
     if (v4l2_ioctl (v4l2object->video_fd, VIDIOC_QUERYCTRL, &control) < 0) {
-      if (errno == EINVAL) {
+      if (errno == EINVAL || errno == ENOTTY) {
         if (n < V4L2_CID_PRIVATE_BASE) {
           GST_DEBUG_OBJECT (e, "skipping control %08x", n);
           /* continue so that we also check private controls */