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/Makefile b/Makefile
index fbd380c..4b6a5e2 100644
--- a/Makefile
+++ b/Makefile
@@ -42,6 +42,7 @@
 	smlc \
 	stp \
 	sysinfo \
+	upf \
 	$(NULL)
 
 NPROC=$(shell nproc 2>/dev/null)