[NET]: Store skb->timestamp as offset to a base timestamp

Reduces skb size by 8 bytes on 64-bit.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/atm/lanai.c b/drivers/atm/lanai.c
index ffe3afa..51ec147 100644
--- a/drivers/atm/lanai.c
+++ b/drivers/atm/lanai.c
@@ -1427,7 +1427,7 @@
 	skb_put(skb, size);
 	vcc_rx_memcpy(skb->data, lvcc, size);
 	ATM_SKB(skb)->vcc = lvcc->rx.atmvcc;
-	do_gettimeofday(&skb->stamp);
+	__net_timestamp(skb);
 	lvcc->rx.atmvcc->push(lvcc->rx.atmvcc, skb);
 	atomic_inc(&lvcc->rx.atmvcc->stats->rx);
     out: