fpga: Add SPDX license identifier

Original-commit: c718ce6cd5b84ceaca50fe02f7ad9e95364472cc

lib/io_port2/LvFpga_Chinch_Interface.v

@@ -10,6 +10,8 @@
 -- (c) 2013 Copyright National Instruments Corporation
 -- All Rights Reserved
 -- National Instruments Internal Information
+--
+-- SPDX-License-Identifier: LGPL-3.0-or-later
 -------------------------------------------------------------------------------
 */