openvswitch: Fix ovs_vport_cmd_del return value on success

If the pointer does not represent an error then the PTR_ERR macro may still
return a nonzero value. The fix is the same as in ovs_vport_cmd_set.
Signed-off-by: NRich Lane <rlane@bigswitch.com>
Signed-off-by: NJesse Gross <jesse@nicira.com>

net/openvswitch/datapath.c

@@ -1772,6 +1772,7 @@ static int ovs_vport_cmd_del(struct sk_buff *skb, struct genl_info *info)
 	if (IS_ERR(reply))
 		goto exit_unlock;
 
+	err = 0;
 	ovs_dp_detach_port(vport);
 
 	genl_notify(reply, genl_info_net(info), info->snd_portid,