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

src/osmo_gsm_tester/obj/ms_srs.py

@@ -43,6 +43,8 @@ def on_register_schemas():
         '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

src/osmo_gsm_tester/templates/srsue.conf.tmpl

@@ -38,6 +38,12 @@ dl_earfcn = 2850,3050
 % else:
 dl_earfcn = 2850
 % endif
+% if ue.get('dl_freq', -1) != -1:
+dl_freq = ${ue.dl_freq}
+% endif
+% if ue.get('ul_freq', -1) != -1:
+ul_freq = ${ue.ul_freq}
+% endif
 freq_offset = ${ue.freq_offset}
 % if int(ue.tx_gain) > 0:
 tx_gain = ${ue.tx_gain}