osmo-trx: Enable multi_arfcn for B200 and only in multiTRX setup

Change-Id: I6a29e1813f0603b00b49b7b7c805be23a72cf0e3
diff --git a/example/resources.conf.rnd b/example/resources.conf.rnd
index 2067efc..dbdf3cc 100644
--- a/example/resources.conf.rnd
+++ b/example/resources.conf.rnd
@@ -28,6 +28,7 @@
     type: uhd
     launch_trx: true
     clock_reference: external
+    multi_arfcn: true
     remote_user: jenkins
     trx_ip: 127.0.0.1
   ciphers: [a5_0, a5_1]