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/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b219a7a..64b385f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1775,7 +1775,7 @@
 	return 0;
 }
 
-int tcp_v4_destroy_sock(struct sock *sk)
+void tcp_v4_destroy_sock(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -1819,8 +1819,6 @@
 	}
 
 	atomic_dec(&tcp_sockets_allocated);
-
-	return 0;
 }
 
 EXPORT_SYMBOL(tcp_v4_destroy_sock);