farsync: fix info leak in ioctl

The fst_get_iface() code fails to initialize the two padding bytes of
struct sync_serial_settings after the ->loopback member. Add an explicit
memset(0) before filling the structure to avoid the info leak.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wan/farsync.c b/drivers/net/wan/farsync.c
index 3f0c4f2..bcfff0d 100644
--- a/drivers/net/wan/farsync.c
+++ b/drivers/net/wan/farsync.c
@@ -1972,6 +1972,7 @@
 	}
 
 	i = port->index;
+	memset(&sync, 0, sizeof(sync));
 	sync.clock_rate = FST_RDL(card, portConfig[i].lineSpeed);
 	/* Lucky card and linux use same encoding here */
 	sync.clock_type = FST_RDB(card, portConfig[i].internalClock) ==