scripts: mailmapper: SPDX license identifier

If the SPDX license identifier is in the first line the shell does not
recognize which interpreter shall be used to execute the script.

Cf. https://www.kernel.org/doc/html/v4.16/process/license-rules.html
for scripts which require the '#!PATH_TO_INTERPRETER' in the first line
(...) the SPDX identifier goes into the second line.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

scripts/mailmapper

@@ -1,5 +1,5 @@
-# SPDX-License-Identifier: GPL-2.0+
 #!/usr/bin/env python2
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (C) 2014, Masahiro Yamada <yamada.m@jp.panasonic.com>