[lchan] Keep track which SAPIs has been established with the BTS

Keep track of which SAPIs have been established either by the
BTS (from the MS) or by us. This can be used by the on-waves
BSC code to figure out if a new request should be made.
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 927c328..94a7081 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -131,6 +131,11 @@
 #define MAX_A5_KEY_LEN	(128/8)
 #define RSL_ENC_ALG_A5(x)	(x+1)
 
+/* is the data link established? who established it? */
+#define LCHAN_SAPI_UNUSED	0
+#define LCHAN_SAPI_MS		1
+#define LCHAN_SAPI_NET		2
+
 struct gsm_lchan {
 	/* The TS that we're part of */
 	struct gsm_bts_trx_ts *ts;
@@ -160,6 +165,9 @@
 
 	struct timer_list T3101;
 
+	/* Established data link layer services */
+	u_int8_t sapis[8];
+
 	/*
 	 * Operations that have a state and might be pending
 	 */