ipaccess.c: Make the compiler happy...

The compiler thinks the variables might not be initialized, we
know it is wrong... but just make it happy.
diff --git a/openbsc/src/input/ipaccess.c b/openbsc/src/input/ipaccess.c
index e98b224..7d7e33c 100644
--- a/openbsc/src/input/ipaccess.c
+++ b/openbsc/src/input/ipaccess.c
@@ -169,7 +169,7 @@
 {
 	struct tlv_parsed tlvp;
 	u_int8_t msg_type = *(msg->l2h);
-	u_int16_t site_id, bts_id, trx_id;
+	u_int16_t site_id = 0, bts_id = 0, trx_id = 0;
 	struct gsm_bts *bts;
 	int ret = 0;