mgcp: Move the rtp state into a struct

Use a struct to group the rtp state for the up and the down
link of the bts.
diff --git a/openbsc/src/mgcp/mgcp_protocol.c b/openbsc/src/mgcp/mgcp_protocol.c
index 5883c15..2a5ce08 100644
--- a/openbsc/src/mgcp/mgcp_protocol.c
+++ b/openbsc/src/mgcp/mgcp_protocol.c
@@ -763,8 +763,8 @@
 	memset(&endp->remote, 0, sizeof(endp->remote));
 	memset(&endp->bts, 0, sizeof(endp->bts));
 
-	endp->net_seq_no = endp->bts_seq_no = 0;
-	endp->net_lost_no = endp->bts_lost_no = 0;
+	memset(&endp->net_state, 0, sizeof(endp->net_state));
+	memset(&endp->bts_state, 0, sizeof(endp->bts_state));
 
 	endp->conn_mode = endp->orig_mode = MGCP_CONN_NONE;
 }