debug log: log all lchan state transitions

Change-Id: Ic70aca65b3796c90ba1a88ea67ac7a2ad9190b69
diff --git a/openbsc/src/libbsc/abis_rsl.c b/openbsc/src/libbsc/abis_rsl.c
index db78fe3..032ff92 100644
--- a/openbsc/src/libbsc/abis_rsl.c
+++ b/openbsc/src/libbsc/abis_rsl.c
@@ -953,6 +953,9 @@
 
 int rsl_lchan_set_state(struct gsm_lchan *lchan, int state)
 {
+	DEBUGP(DRSL, "%s state %s -> %s\n",
+	       gsm_lchan_name(lchan), gsm_lchans_name(lchan->state),
+	       gsm_lchans_name(state));
 	lchan->state = state;
 	return 0;
 }