ms_srs: add resource scheme to configure fixed DL and UL freq

this config option overwrites the EARFCN config that is typically
used to tell the UE the bands to scan for cells. When custom
frequencies are used, this option allows to set them explicitly.

Change-Id: Ice070ea6755e273d916db2dc941068d33bbe206a
diff --git a/src/osmo_gsm_tester/obj/ms_srs.py b/src/osmo_gsm_tester/obj/ms_srs.py
index 767f887..041fd91 100644
--- a/src/osmo_gsm_tester/obj/ms_srs.py
+++ b/src/osmo_gsm_tester/obj/ms_srs.py
@@ -43,6 +43,8 @@
         'rx_gain': schema.INT,
         'freq_offset': schema.INT,
         'force_ul_amplitude': schema.STR,
+        'dl_freq': schema.STR,
+        'ul_freq': schema.STR
         }
     for key, val in RunNode.schema().items():
         resource_schema['run_node.%s' % key] = val