add upf/ to test osmo-upf

So far testing only PFCP interaction without real GTP traffic.

Related: SYS#5599
Change-Id: If67819dea785597841f21d8c444cb4866cfde571
diff --git a/upf/README.txt b/upf/README.txt
new file mode 100644
index 0000000..9f1eced
--- /dev/null
+++ b/upf/README.txt
@@ -0,0 +1,4 @@
+Integration Tests for OsmoUPF
+-----------------------------
+
+This test suite tests OsmoUPF, emulating a Control Plane Function.