srs{enb,ue}: add rf_dev_sync option to config templates

pass-through the option so they can be used in templates

just concatenate with rf_dev_args for srsLTE eNB/UE, arguments
parsing will handle them

Change-Id: I3818026c159780f29968888f547163cdf730afad
diff --git a/src/osmo_gsm_tester/obj/enb_srs.py b/src/osmo_gsm_tester/obj/enb_srs.py
index ad92af5..63e5d7c 100644
--- a/src/osmo_gsm_tester/obj/enb_srs.py
+++ b/src/osmo_gsm_tester/obj/enb_srs.py
@@ -191,6 +191,7 @@
         config.overlay(values, dict(enb={'enable_pcap': self.enable_pcap}))
 
         config.overlay(values, dict(enb={'enable_dl_awgn': util.str2bool(values['enb'].get('enable_dl_awgn', 'false'))}))
+        config.overlay(values, dict(enb={'rf_dev_sync': values['enb'].get('rf_dev_sync', None)}))
 
         self._additional_args = []
         for add_args in values['enb'].get('additional_args', []):