debian: Add systemd service file

Provide a modern systemd service file for the osmo-stp. The sysvinit
file is quite basic and doesn't signal syntax errors nicely. Let us
embrace the future.

Change-Id: Ic0cc0f17d442aa0ad38de9f0cf8aeb14121938de
diff --git a/debian/control b/debian/control
index 6d23a4e..0f4c286 100644
--- a/debian/control
+++ b/debian/control
@@ -2,7 +2,7 @@
 Section: net
 Priority: optional
 Maintainer: Holger Hans Peter Freyther <holger@freyther.de>
-Build-Depends: debhelper (>= 9), autotools-dev, pkg-config, libosmocore-dev, libosmo-sccp-dev, dh-autoreconf, libsnmp-dev, libsctp-dev
+Build-Depends: debhelper (>= 9), autotools-dev, pkg-config, libosmocore-dev, libosmo-sccp-dev, dh-autoreconf, dh-systemd (>= 1.5), libsnmp-dev, libsctp-dev
 Standards-Version: 3.9.6
 Homepage: http://openbsc.osmocom.org/
 Vcs-Git: git://bs11-abis.gnumonks.org/cellmgr-ng.git
diff --git a/debian/osmo-stp.service b/debian/osmo-stp.service
new file mode 100644
index 0000000..cef1085
--- /dev/null
+++ b/debian/osmo-stp.service
@@ -0,0 +1,11 @@
+[Unit]
+Description=Osmocom osmo-stp bridge
+
+[Service]
+Type=simple
+ExecStart=/usr/sbin/osmo-stp -c /etc/osmocom/osmo-stp.cfg
+Restart=always
+RestartSec=2
+
+[Install]
+WantedBy=multi-user.target