move RTP socket information from timeslot to lchan

With ip.access, in case of TCH/H, we have one RTP stream for each half-slot
(lchan), not just one per on-air timeslot.  This is quite different from
a classic BTS where the TRAU frames of the two TCH/H channels would be
part of the same 16k sub-slot in a E1 timeslot.
diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index fcd623f..bd7b79b 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -185,6 +185,14 @@
 
 	/* use count. how many users use this channel */
 	unsigned int use_count;
+
+	struct {
+		u_int32_t bound_ip;
+		u_int16_t bound_port;
+		u_int8_t rtp_payload2;
+		u_int16_t conn_id;
+		struct rtp_socket *rtp_socket;
+	} abis_ip;
 };
 
 struct gsm_e1_subslot {
@@ -212,13 +220,6 @@
 
 	/* To which E1 subslot are we connected */
 	struct gsm_e1_subslot e1_link;
-	struct {
-		u_int32_t bound_ip;
-		u_int16_t bound_port;
-		u_int8_t rtp_payload2;
-		u_int16_t conn_id;
-		struct rtp_socket *rtp_socket;
-	} abis_ip;
 
 	struct gsm_lchan lchan[TS_MAX_LCHAN];
 };