icmpv6_filter: fix "_hdr" incorrectly being a pointer

"_hdr" should hold the ICMPv6 header while "hdr" is the pointer to it.
This worked by accident.
Signed-off-by: Werner Almesberger <werner@almesberger.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/raw.c

@@ -108,7 +108,7 @@ static struct sock *__raw_v6_lookup(struct net *net, struct sock *sk,
  */
 static int icmpv6_filter(const struct sock *sk, const struct sk_buff *skb)
 {
-	struct icmp6hdr *_hdr;
+	struct icmp6hdr _hdr;
 	const struct icmp6hdr *hdr;
 
 	hdr = skb_header_pointer(skb, skb_transport_offset(skb),