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/grc/trx/gsm_trx_burst_if.xml b/grc/trx/gsm_trx_burst_if.xml
index 99427b3..49979a3 100644
--- a/grc/trx/gsm_trx_burst_if.xml
+++ b/grc/trx/gsm_trx_burst_if.xml
@@ -3,7 +3,7 @@
   <name>TRX Burst Interface</name>
   <key>gsm_trx_burst_if</key>
   <import>import grgsm</import>
-  <make>grgsm.trx_burst_if($remote_addr, $base_port)</make>
+  <make>grgsm.trx_burst_if($bind_addr, $remote_addr, $base_port)</make>
 
   <param>
     <name>base_port</name>
@@ -13,6 +13,13 @@
   </param>
 
   <param>
+    <name>bind_addr</name>
+    <key>bind_addr</key>
+    <value>0.0.0.0</value>
+    <type>string</type>
+  </param>
+
+  <param>
     <name>remote_addr</name>
     <key>remote_addr</key>
     <value>127.0.0.1</value>