trx/ctrl_if.py: use relative import for UDPLink

Change-Id: If4b00f6332461d3c37cde5a1f724906ca3d3a30f
diff --git a/python/trx/ctrl_if.py b/python/trx/ctrl_if.py
index fc43b7f..1a7c0c3 100644
--- a/python/trx/ctrl_if.py
+++ b/python/trx/ctrl_if.py
@@ -22,7 +22,7 @@
 # with this program; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-from grgsm.trx import UDPLink
+from udp_link import UDPLink
 
 class CTRLInterface(UDPLink):
 	def handle_rx(self, data, remote):