net: change proto destroy method to return void

Change struct proto destroy function pointer to return void.  Noticed
by Al Viro.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/udp_impl.h b/net/ipv6/udp_impl.h
index 321b81a..92dd7da 100644
--- a/net/ipv6/udp_impl.h
+++ b/net/ipv6/udp_impl.h
@@ -29,7 +29,7 @@
 			      struct msghdr *msg, size_t len,
 			      int noblock, int flags, int *addr_len);
 extern int	udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb);
-extern int	udpv6_destroy_sock(struct sock *sk);
+extern void	udpv6_destroy_sock(struct sock *sk);
 
 #ifdef CONFIG_PROC_FS
 extern int	udp6_seq_show(struct seq_file *seq, void *v);