[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/he.c b/drivers/atm/he.c
index 28250c9..fde9334 100644
--- a/drivers/atm/he.c
+++ b/drivers/atm/he.c
@@ -1886,7 +1886,7 @@
 		if (rx_skb_reserve > 0)
 			skb_reserve(skb, rx_skb_reserve);
 
-		do_gettimeofday(&skb->stamp);
+		__net_timestamp(skb);
 
 		for (iov = he_vcc->iov_head;
 				iov < he_vcc->iov_tail; ++iov) {