net-timestamp: Make the clone operation stand-alone from phy timestamping

The phy timestamping takes a different path than the regular timestamping
does in that it will create a clone first so that the packets needing to be
timestamped can be placed in a queue, or the context block could be used.

In order to support these use cases I am pulling the core of the code out
so it can be used in other drivers beyond just phy devices.

In addition I have added a destructor named sock_efree which is meant to
provide a simple way for dropping the reference to skb exceptions that
aren't part of either the receive or send windows for the socket, and I
have removed some duplication in spots where this destructor could be used
in place of sock_edemux.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
index d5991ac..87648b3 100644
--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -1148,7 +1148,7 @@
 		kfree_skb(skb);
 
 	while ((skb = skb_dequeue(&dp83640->tx_queue)) != NULL)
-		skb_complete_tx_timestamp(skb, NULL);
+		kfree_skb(skb);
 
 	clock = dp83640_clock_get(dp83640->clock);
 
@@ -1405,7 +1405,7 @@
 
 	case HWTSTAMP_TX_ONESTEP_SYNC:
 		if (is_sync(skb, type)) {
-			skb_complete_tx_timestamp(skb, NULL);
+			kfree_skb(skb);
 			return;
 		}
 		/* fall through */
@@ -1416,7 +1416,7 @@
 
 	case HWTSTAMP_TX_OFF:
 	default:
-		skb_complete_tx_timestamp(skb, NULL);
+		kfree_skb(skb);
 		break;
 	}
 }