Fix transaction_id displayed in debug message

In SMS debug messages, we always display the transaction ID
as if we were 'sending' the message.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index a87c6ed..38f585b 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -906,7 +906,7 @@
 		return -EIO;
 		/* FIXME: send some error message */
 
-	DEBUGP(DSMS, "trans_id=%x ", gh->proto_discr >> 4);
+	DEBUGP(DSMS, "trans_id=%x ", transaction_id);
 	trans = trans_find_by_id(lchan->subscr, GSM48_PDISC_SMS,
 				 transaction_id);
 	if (!trans) {