Debian: Add systemd service files for osmo-sgsn and osmo-gbproxy

Change-Id: I5a5a80bb19c521e8f20241ed8c02d65b4c937f23
diff --git a/debian/osmo-gbproxy.service b/debian/osmo-gbproxy.service
new file mode 120000
index 0000000..d23c649
--- /dev/null
+++ b/debian/osmo-gbproxy.service
@@ -0,0 +1 @@
+../contrib/systemd/osmo-gbproxy.service
\ No newline at end of file
diff --git a/debian/osmo-sgsn.service b/debian/osmo-sgsn.service
new file mode 120000
index 0000000..de22d90
--- /dev/null
+++ b/debian/osmo-sgsn.service
@@ -0,0 +1 @@
+../contrib/systemd/osmo-sgsn.service
\ No newline at end of file