doc: ABI scripts: add a SPDX header file

released under GPL v2.
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/get_abi.pl

 #!/usr/bin/perl
+# SPDX-License-Identifier: GPL-2.0
 
 use strict;
 use Pod::Usage;