net: correct off-by-one write allocations reports

commit 2b85a34e911bf483c27cfdd124aeb1605145dc80
(net: No more expensive sock_hold()/sock_put() on each tx)
changed initial sk_wmem_alloc value.

We need to take into account this offset when reporting
sk_wmem_alloc to user, in PROC_FS files or various
ioctls (SIOCOUTQ/TIOCOUTQ)

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index 02b9baa..0250e06 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -337,7 +337,7 @@
 		if (sk->sk_state == BT_LISTEN)
 			return -EINVAL;
 
-		amount = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);
+		amount = sk->sk_sndbuf - sk_wmem_alloc_get(sk);
 		if (amount < 0)
 			amount = 0;
 		err = put_user(amount, (int __user *) arg);