ipv6: Remove duplicate statements

This statement is repeated with the initialization statement
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: luo penghao <luo.penghao@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/exthdrs.c

@@ -686,7 +686,6 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	struct net *net = dev_net(skb->dev);
 	int accept_source_route = net->ipv6.devconf_all->accept_source_route;
 
-	idev = __in6_dev_get(skb->dev);
 	if (idev && accept_source_route > idev->cnf.accept_source_route)
 		accept_source_route = idev->cnf.accept_source_route;