transaction: change arguments of trans_find_by_sm_rp_mr()

The need to pass a pointer to RAN connection in order to find
a transaction limits possible use cases of trans_find_by_sm_rp_mr(),
e.g. when we need to find a transaction, but RAN connection is not
established yet.

Moreover, the pointer to RAN connection was only used to obtain
pointers to gsm_network and vlr_subscr, so we can just
pass them directly.

Change-Id: I093f36d63e671e50e54fc6236e97a777cc6da77b
diff --git a/src/libmsc/transaction.c b/src/libmsc/transaction.c
index 70a39e8..7c91c92 100644
--- a/src/libmsc/transaction.c
+++ b/src/libmsc/transaction.c
@@ -72,15 +72,15 @@
 }
 
 /*! Find a transaction by SM-RP-MR (RP Message Reference)
- * \param[in] conn Connection in which we want to find transaction
+ * \param[in] net Network in which we should search
+ * \param[in] vsub Subscriber for which we should search
  * \param[in] sm_rp_mr RP Message Reference (see GSM TS 04.11, section 8.2.3)
  * \returns Matching transaction, NULL otherwise
  */
-struct gsm_trans *trans_find_by_sm_rp_mr(const struct ran_conn *conn,
+struct gsm_trans *trans_find_by_sm_rp_mr(const struct gsm_network *net,
+					 const struct vlr_subscr *vsub,
 					 uint8_t sm_rp_mr)
 {
-	struct gsm_network *net = conn->network;
-	struct vlr_subscr *vsub = conn->vsub;
 	struct gsm_trans *trans;
 
 	llist_for_each_entry(trans, &net->trans_list, entry) {