Fix AVDTP suspend while closing

We should reject any suspend request if we've already started the close
procedure for a stream.
diff --git a/audio/avdtp.c b/audio/avdtp.c
index 41ded83..f6441c7 100644
--- a/audio/avdtp.c
+++ b/audio/avdtp.c
@@ -3249,7 +3249,7 @@
 	if (!g_slist_find(session->streams, stream))
 		return -EINVAL;
 
-	if (stream->lsep->state <= AVDTP_STATE_OPEN)
+	if (stream->lsep->state <= AVDTP_STATE_OPEN || stream->close_int)
 		return -EINVAL;
 
 	memset(&req, 0, sizeof(req));