[si] Make it possible to set the NECI value...

Allow to configure the NECI value... and change code
that is relying on the NECI value.
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index de0f484..2d00603 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -1133,8 +1133,8 @@
 
 	/* determine channel type (SDCCH/TCH_F/TCH_H) based on
 	 * request reference RA */
-	lctype = get_ctype_by_chreq(bts, rqd_ref->ra);
-	chreq_reason = get_reason_by_chreq(bts, rqd_ref->ra);
+	lctype = get_ctype_by_chreq(bts, rqd_ref->ra, bts->network->neci);
+	chreq_reason = get_reason_by_chreq(bts, rqd_ref->ra, bts->network->neci);
 
 	/* check availability / allocate channel */
 	lchan = lchan_alloc(bts, lctype);