ipv6: sr: fix double free of skb after handling invalid SRH

The icmpv6_param_prob() function already does a kfree_skb(),
this patch removes the duplicate one.

Fixes: 1ababeb ("ipv6: implement dataplane support for rthdr type 4 (Segment Routing Header)")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Lebrun <david.lebrun@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/exthdrs.c

@@ -388,7 +388,6 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 				  ((&hdr->segments_left) -
 				   skb_network_header(skb)));
-		kfree_skb(skb);
 		return -1;
 	}