contrib: Add osmo-mgw systemd service

Change-Id: Ic89815dc4ef8dff8a9d8541b61212ab8d4837712
diff --git a/contrib/systemd/osmo-mgw.service b/contrib/systemd/osmo-mgw.service
new file mode 100644
index 0000000..f75277e
--- /dev/null
+++ b/contrib/systemd/osmo-mgw.service
@@ -0,0 +1,11 @@
+[Unit]
+Description=Osmocom Media Gateway (MGW)
+
+[Service]
+Type=simple
+Restart=always
+ExecStart=/usr/bin/osmo-mgw -s -c /etc/osmocom/osmo-mgw.cfg
+RestartSec=2
+
+[Install]
+WantedBy=multi-user.target