[debug] Move subscr_get_by_tmsi below the debug statement (Andreas Eversberg)

subscr_get_by_tmsi might log as well and then the order of
debugging it not as clear as it could be.
diff --git a/src/gsm_04_08.c b/src/gsm_04_08.c
index d585aae..fd47d8b 100644
--- a/src/gsm_04_08.c
+++ b/src/gsm_04_08.c
@@ -797,10 +797,11 @@
 	}
 
 	mi_to_string(mi_string, sizeof(mi_string), mi, mi_len);
-	subscr = subscr_get_by_tmsi(mi_string);
 	DEBUGPC(DMM, "serv_type=0x%02x mi_type=0x%02x M(%s)\n",
 		req->cm_service_type, mi_type, mi_string);
 
+	subscr = subscr_get_by_tmsi(mi_string);
+
 	/* FIXME: if we don't know the TMSI, inquire abit IMSI and allocate new TMSI */
 	if (!subscr)
 		return gsm48_tx_mm_serv_rej(msg->lchan,