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/ipv4/udp.c b/net/ipv4/udp.c
index 355e6d6..eba790d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1253,12 +1253,11 @@
 	return __udp4_lib_rcv(skb, udp_hash, IPPROTO_UDP);
 }
 
-int udp_destroy_sock(struct sock *sk)
+void udp_destroy_sock(struct sock *sk)
 {
 	lock_sock(sk);
 	udp_flush_pending_frames(sk);
 	release_sock(sk);
-	return 0;
 }
 
 /*