Introduce RFemu stdin implementation for srsENB

Change-Id: I5487dec3691cbf424306369f94f337ed34a10c70
diff --git a/sysmocom/defaults.conf b/sysmocom/defaults.conf
index ed0b575..419c3a4 100644
--- a/sysmocom/defaults.conf
+++ b/sysmocom/defaults.conf
@@ -148,6 +148,11 @@
   tx_gain: 80
   rx_gain: 40
   log_all_level: warning
+  cell_list:
+   - dl_rfemu:
+       type: srsenb_stdin
+   - dl_rfemu:
+       type: srsenb_stdin
 
 amarisoftenb:
   num_prb: 100