Use 04.08 IMM ASS REJECT in case we run out of channels

If the user has a non-zero 'timer t3122' in the config file, we will
send an IMM ASS REJECT in case we run out of resources.
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index c27db85..b5f17ac 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -710,6 +710,7 @@
 	int T3115;
 	int T3117;
 	int T3119;
+	int T3122;
 	int T3141;
 
 	/* Radio Resource Location Protocol (TS 04.31) */