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/python/trx/radio_if.py b/python/trx/radio_if.py
index 2648cc9..25a35a5 100644
--- a/python/trx/radio_if.py
+++ b/python/trx/radio_if.py
@@ -81,7 +81,8 @@
 	def __init__(self, phy_args, phy_sample_rate,
 			phy_rx_gain, phy_tx_gain, phy_ppm,
 			phy_rx_antenna, phy_tx_antenna,
-			trx_remote_addr, trx_base_port):
+			trx_remote_addr, trx_base_port,
+			trx_bind_addr = "0.0.0.0"):
 
 		print("[i] Init Radio interface")
 
@@ -95,8 +96,8 @@
 
 		# TRX Burst Interface
 		self.trx_burst_if = grgsm.trx_burst_if(
-			trx_remote_addr, str(trx_base_port))
-
+			trx_bind_addr, trx_remote_addr,
+			str(trx_base_port))
 
 		# RX path definition
 		self.phy_src = uhd.usrp_source(phy_args,