gsm_trx_burst_if: allow to customize the bind address

Pleviously remote address for DATA interface was also used as the
bind address, what is definitely wrong. Let's change the API a bit
in order to allow one to specify a custom bind address.

Change-Id: I6e5f7b7119ac454217b8dd04f9ee0dd3b23972b6
diff --git a/include/grgsm/trx/trx_burst_if.h b/include/grgsm/trx/trx_burst_if.h
index 0e7a35a..9277dc5 100644
--- a/include/grgsm/trx/trx_burst_if.h
+++ b/include/grgsm/trx/trx_burst_if.h
@@ -48,6 +48,7 @@
        * creating new instances.
        */
       static sptr make(
+        const std::string &bind_addr,
         const std::string &remote_addr,
         const std::string &base_port);
     };