[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/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 40b2195..d6da093 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -1087,7 +1087,7 @@
 	memcpy(ev->data, data, dlen);
 
 	bt_cb(skb)->incoming = 1;
-	do_gettimeofday(&skb->stamp);
+	__net_timestamp(skb);
 
 	bt_cb(skb)->pkt_type = HCI_EVENT_PKT;
 	skb->dev = (void *) hdev;