srsLTE: Support configuring different RF backends

Before this patch, only virtual RF through ZeroMQ was supported.
This patch allows configuring srsUE and srsENB to use a real SDR with
UHD/SoapySDR backend connected through a physical RF network, while
still keeping compatibility to run on virtual RF ZeroMQ network, based
on the resources used (controlled by scenarios). For instance, one can
first run a suite through the phyisical RF (using 2 UHD-controlled SDRs)
and afterwards with ZeroMQ using the following default-suites.conf:

- 4g:srsenb-rftype-uhd+srsue-rftype-uhd
- 4g:srsenb-rftype-zmq+srsue-rftype-zmq

Change-Id: I7dbbe328f4c0225fe74e878bb2da13fe39ccf049
diff --git a/src/osmo_gsm_tester/templates/srsue.conf.tmpl b/src/osmo_gsm_tester/templates/srsue.conf.tmpl
index 5e5676d..eef5a7e 100644
--- a/src/osmo_gsm_tester/templates/srsue.conf.tmpl
+++ b/src/osmo_gsm_tester/templates/srsue.conf.tmpl
@@ -39,13 +39,15 @@
 #nof_radios = 1
 #nof_rx_ant = 1
 
+device_name = ${ue.rf_dev_type}
+
 # For best performance in 2x2 MIMO and >= 15 MHz use the following device_args settings:
 #     USRP B210: num_recv_frames=64,num_send_frames=64
 
 # For best performance when BW<5 MHz (25 PRB), use the following device_args settings:
 #     USRP B210: send_frame_size=512,recv_frame_size=512
 
-#device_args = auto
+device_args = ${ue.rf_dev_args}
 #time_adv_nsamples = auto
 #burst_preamble_us = auto
 #continuous_tx     = auto