[media] vb2: fix plane index sanity check in vb2_plane_cookie()

It's also invalid when plane_no is equal to vb->num_planes
Signed-off-by: Zhaowei Yuan <zhaowei.yuan@samsung.com>
Cc: stable@vger.kernel.org      # for v3.7 and up
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/videobuf2-core.c

@@ -1130,7 +1130,7 @@ EXPORT_SYMBOL_GPL(vb2_plane_vaddr);
  */
 void *vb2_plane_cookie(struct vb2_buffer *vb, unsigned int plane_no)
 {
-	if (plane_no > vb->num_planes || !vb->planes[plane_no].mem_priv)
+	if (plane_no >= vb->num_planes || !vb->planes[plane_no].mem_priv)
 		return NULL;
 
 	return call_ptr_memop(vb, cookie, vb->planes[plane_no].mem_priv);