Implement VTY configuration to control Early Classmark Sending

The SI3 rest octests contain a flag that indicates if early classmark
sending is allowed in this cell or not.  So far we always set this to
one, now it is configurable using the 'early-classmark-sending' command
at the VTY node.

Change-Id: Ia0b1cc5ab45673f3da70c59ae8917eba343f9862
diff --git a/openbsc/src/libbsc/system_information.c b/openbsc/src/libbsc/system_information.c
index e71490e..a2dd827 100644
--- a/openbsc/src/libbsc/system_information.c
+++ b/openbsc/src/libbsc/system_information.c
@@ -764,6 +764,8 @@
 	} else {
 		si_info.si2quater_indicator = 0;
 	}
+	si_info.early_cm_ctrl = bts->early_classmark_allowed;
+
 	/* SI3 Rest Octets (10.5.2.34), containing
 		CBQ, CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, PENALTY_TIME
 		Power Offset, 2ter Indicator, Early Classmark Sending,