add enable_snat configuration

charts/oai-5g-core/oai-5g-basic/config.yaml

@@ -172,7 +172,7 @@ smf:
 upf:
   support_features:
     enable_bpf_datapath: no    # If "on": BPF is used as datapath else simpleswitch is used, DEFAULT= off
-    enable_snat: yes           # If "on": Source natting is done for UE, DEFAULT= off
+    enable_snat: @ENABLE_SNAT@           # If "on": Source natting is done for UE, DEFAULT= off
   remote_n6_gw: 127.0.0.1      # Dummy host since simple-switch does not use N6 GW
   upf_info:
     sNssaiUpfInfoList: