net: ipv6: remove unused inline function ip6_set_txhash

commit 877d1f62 ("net: Set sk_txhash from a random number")
left behind this, remove it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -908,7 +908,6 @@ static inline int ip6_default_np_autolabel(struct net *net)
 	}
 }
 #else
-static inline void ip6_set_txhash(struct sock *sk) { }
 static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
 					__be32 flowlabel, bool autolabel,
 					struct flowi6 *fl6)