Add SPDX-License-Identifier to all source files

Change-Id: I9f2bc8c5d8a2c0bb0dd6caa4de5e2cb11be210e7
diff --git a/debian/copyright b/debian/copyright
index d6ebceb..41573fe 100644
--- a/debian/copyright
+++ b/debian/copyright
@@ -9,7 +9,7 @@
            2010,2014 On-Waves
            2011-2014 Pablo Neira Ayuso <pablo@gnumonks.org>
            2012      Tobias Engel
-           2014      Sysmocom s.f.m.c. GmBH
+           2014      sysmocom - s.f.m.c. GmBH
 License: AGPL-3+
 
 Files: src/input/lapd.c