util/spkmodem-recv: re-add full license header

i forked spkmodem-recv from coreboot, who forked it from
gnu grub. gnu grub's version has the full header, with
copyright declared as belonging to the fsf

coreboot made changes after forking it, and later replaced
the license declaration with an equivalent SPDX header, but
they also removed the FSF's copyright declaration, which by
itself does not void the declaration

anyway, i just feel better re-adding the full declaration.
make it so!

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/spkmodem_recv/spkmodem-recv.c

@@ -1,5 +1,20 @@
 /* spkmodem-recv.c - decode spkmodem signals */
-/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ *  Copyright (C) 2013  Free Software Foundation, Inc.
+ *
+ *  spkmodem-recv is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  spkmodem-recv is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with spkmodem-recv.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
 #include <err.h>
 #include <errno.h>