gsm: lapd_core: Log timeout used upon start of T200

The timeout is calculated dynamically in t200_by_lchan() based on FN
advance value estimated by bts_get_avg_fn_advance(), so it's informative
to have the final value printed out.

Change-Id: Ib50a9c23de881c66c9218833703cc41101e06bfd
diff --git a/src/gsm/lapd_core.c b/src/gsm/lapd_core.c
index 19dff4f..a0f3c2b 100644
--- a/src/gsm/lapd_core.c
+++ b/src/gsm/lapd_core.c
@@ -203,7 +203,8 @@
 {
 	if (osmo_timer_pending(&dl->t200))
 		return;
-	LOGP(DLLAPD, LOGL_INFO, "start T200 (dl=%p)\n", dl);
+	LOGP(DLLAPD, LOGL_INFO, "start T200 (dl=%p, timeout=%d.%06ds)\n",
+	     dl, dl->t200_sec, dl->t200_usec);
 	osmo_timer_schedule(&dl->t200, dl->t200_sec, dl->t200_usec);
 }