fix uninitialized vars warnings with -Os

Change-Id: I15a16ba9751b6b612bac61a160b5da394ed2e15c
Signed-off-by: Benoît Ganne <bganne@kalrayinc.com>
diff --git a/vnet/vnet/ip/ip6_neighbor.c b/vnet/vnet/ip/ip6_neighbor.c
index 70d77a5..957e35b 100644
--- a/vnet/vnet/ip/ip6_neighbor.c
+++ b/vnet/vnet/ip/ip6_neighbor.c
@@ -1894,8 +1894,8 @@
   ip6_radv_t *radv_info; 
   vlib_frame_t * f = 0; 
   u32 n_this_frame = 0;
-  u32 n_left_to_next;
-  u32 * to_next;
+  u32 n_left_to_next = 0;
+  u32 * to_next = 0;
   u32 bo0; 
   icmp6_router_solicitation_header_t * h0;
   vlib_buffer_t * b0;