Add support to enable EGPRS

Change-Id: I682f0c1b4cb97b704d646f18f54e748baaefd677
diff --git a/example/defaults.conf b/example/defaults.conf
index 1855883..eee17b1 100644
--- a/example/defaults.conf
+++ b/example/defaults.conf
@@ -31,6 +31,7 @@
   stream_id: 255
   osmobsc_bts_type: sysmobts
   channel_allocator: ascending
+  gprs_mode: gprs
   num_trx: 1
   max_trx: 1
   trx_list: