apps/grgsm_trx: introduce bind address option

The new option (-b --bind-addr) allows one to specify the bind
address for both DATA and CTRL interfaces. By default, '0.0.0.0'
is used, so there are no restrictions for the L1 source address.

Change-Id: I3339f686b53db07cfd1bff9a516f4bdc28058cd9
diff --git a/python/trx/radio_if.py b/python/trx/radio_if.py
index 25a35a5..1c7f003 100644
--- a/python/trx/radio_if.py
+++ b/python/trx/radio_if.py
@@ -81,8 +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_bind_addr = "0.0.0.0"):
+			trx_bind_addr, trx_remote_addr,
+			trx_base_port):
 
 		print("[i] Init Radio interface")