netlink: Fix build with mmap disabled.

net/netlink/diag.c: In function 'sk_diag_put_rings_cfg':
net/netlink/diag.c:28:17: error: 'struct netlink_sock' has no member named 'pg_vec_lock'
net/netlink/diag.c:29:29: error: 'struct netlink_sock' has no member named 'rx_ring'
net/netlink/diag.c:31:30: error: 'struct netlink_sock' has no member named 'tx_ring'
net/netlink/diag.c:33:19: error: 'struct netlink_sock' has no member named 'pg_vec_lock'

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/diag.c

@@ -7,6 +7,7 @@
 
 #include "af_netlink.h"
 
+#ifdef CONFIG_NETLINK_MMAP
 static int sk_diag_put_ring(struct netlink_ring *ring, int nl_type,
 			    struct sk_buff *nlskb)
 {
@@ -34,6 +35,12 @@ static int sk_diag_put_rings_cfg(struct sock *sk, struct sk_buff *nlskb)
 
 	return ret;
 }
+#else
+static int sk_diag_put_rings_cfg(struct sock *sk, struct sk_buff *nlskb)
+{
+	return 0;
+}
+#endif
 
 static int sk_diag_dump_groups(struct sock *sk, struct sk_buff *nlskb)
 {