[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/firestream.c b/drivers/atm/firestream.c
index b078fa5..5821974 100644
--- a/drivers/atm/firestream.c
+++ b/drivers/atm/firestream.c
@@ -815,7 +815,7 @@
 				skb_put (skb, qe->p1 & 0xffff); 
 				ATM_SKB(skb)->vcc = atm_vcc;
 				atomic_inc(&atm_vcc->stats->rx);
-				do_gettimeofday(&skb->stamp);
+				__net_timestamp(skb);
 				fs_dprintk (FS_DEBUG_ALLOC, "Free rec-skb: %p (pushed)\n", skb);
 				atm_vcc->push (atm_vcc, skb);
 				fs_dprintk (FS_DEBUG_ALLOC, "Free rec-d: %p\n", pe);