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/resource.py b/src/osmo_gsm_tester/resource.py
index 0804591..e8ca859 100644
--- a/src/osmo_gsm_tester/resource.py
+++ b/src/osmo_gsm_tester/resource.py
@@ -89,7 +89,8 @@
         'enb[].type': schema.STR,
         'enb[].remote_user': schema.STR,
         'enb[].addr': schema.IPV4,
-        'enb[].band': schema.BAND,
+        'enb[].rf_dev_type': schema.STR,
+        'enb[].rf_dev_args': schema.STR,
         'arfcn[].arfcn': schema.INT,
         'arfcn[].band': schema.BAND,
         'modem[].type': schema.STR,
@@ -102,6 +103,8 @@
         'modem[].addr': schema.IPV4,
         'modem[].ciphers[]': schema.CIPHER,
         'modem[].features[]': schema.MODEM_FEATURE,
+        'modem[].rf_dev_type': schema.STR,
+        'modem[].rf_dev_args': schema.STR,
         'osmocon_phone[].serial_device': schema.STR,
     }