isisd/isis_dlpi: Fix warning

'fd' may be used uninitialized. Init to -1

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/isisd/isis_dlpi.c b/isisd/isis_dlpi.c
index d16667e..b583d10 100644
--- a/isisd/isis_dlpi.c
+++ b/isisd/isis_dlpi.c
@@ -303,7 +303,7 @@
 static int
 open_dlpi_dev (struct isis_circuit *circuit)
 {
-  int fd, unit, retval;
+  int fd = -1, unit, retval;
   char devpath[MAXPATHLEN];
   dl_info_ack_t *dia = (dl_info_ack_t *)dlpi_ctl;
   ssize_t acklen;