ip_gre: remove an extra dst_release()

commit 68c33163 (v4 GRE: Add TCP segmentation offload for GRE)
introduced a bug in error path.

dst is attached to skb, so will be released when skb is freed.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Acked-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ip_gre.c

@@ -1006,10 +1006,8 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 
 			if (skb_has_shared_frag(skb)) {
 				err = __skb_linearize(skb);
-				if (err) {
-					ip_rt_put(rt);
+				if (err)
 					goto tx_error;
-				}
 			}
 
 			*ptr = 0;