UNIX: remove unused declaration of sysctl_unix_max_dgram_qlen

Signed-off-by: Denis V. Lunev <den@openvz.org>
--
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -59,7 +59,6 @@ struct unix_sock {
 #define unix_sk(__sk) ((struct unix_sock *)__sk)
 
 #ifdef CONFIG_SYSCTL
-extern int sysctl_unix_max_dgram_qlen;
 extern int unix_sysctl_register(struct net *net);
 extern void unix_sysctl_unregister(struct net *net);
 #else