fpga: use SPDX

Replace GPLv2 boilerplate with SPDX in FPGA code that came from me or
from Altera.

Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/fpga/fpga-region.h

@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
 #ifndef _FPGA_REGION_H
 #define _FPGA_REGION_H