bridge: Add const to dummy br_netpoll_send_skb

The version of br_netpoll_send_skb used when netpoll is off is
missing a const thus causing a warning.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index f6bc979..07cf57b 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -305,7 +305,7 @@
 	return NULL;
 }
 
-static inline void br_netpoll_send_skb(struct net_bridge_port *p,
+static inline void br_netpoll_send_skb(const struct net_bridge_port *p,
 				       struct sk_buff *skb)
 {
 }