enb_amarisoft: add rf_dev_sync option to specify the sync type

this allows to specify "external_clock" for example to use
the external REF input of an USRP

Change-Id: Ie066993440840cbd2c18e8f0c0c577b92ac7092d
diff --git a/src/osmo_gsm_tester/obj/enb_amarisoft.py b/src/osmo_gsm_tester/obj/enb_amarisoft.py
index 0f8944f..1fc4485 100644
--- a/src/osmo_gsm_tester/obj/enb_amarisoft.py
+++ b/src/osmo_gsm_tester/obj/enb_amarisoft.py
@@ -214,6 +214,7 @@
         # different cfg namespace 'trx'. Copy needed values over there:
         config.overlay(values, dict(trx=dict(rf_dev_type=values['enb'].get('rf_dev_type', None),
                                              rf_dev_args=values['enb'].get('rf_dev_args', None),
+                                             rf_dev_sync=values['enb'].get('rf_dev_sync', None),
                                              rx_gain=values['enb'].get('rx_gain', None),
                                              tx_gain=values['enb'].get('tx_gain', None),
                                             )))