openvswitch: fix odd_ptr_err.cocci warnings

net/openvswitch/vport-gre.c:188:5-11: inconsistent IS_ERR and PTR_ERR, PTR_ERR on line 189

 PTR_ERR should access the value just tested by IS_ERR

Semantic patch information:
 There can be false positives in the patch case, where it is the call
 IS_ERR that is wrong.

Generated by: scripts/coccinelle/tests/odd_ptr_err.cocci

CC: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: NFengguang Wu <fengguang.wu@intel.com>
Acked-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/openvswitch/vport-gre.c

@@ -186,7 +186,7 @@ static int gre_tnl_send(struct vport *vport, struct sk_buff *skb)
 	/* Push Tunnel header. */
 	skb = __build_header(skb, tunnel_hlen);
 	if (IS_ERR(skb)) {
-		err = PTR_ERR(rt);
+		err = PTR_ERR(skb);
 		skb = NULL;
 		goto err_free_rt;
 	}