net: simplify flags for tx timestamping

This patch removes the abstraction introduced by the union skb_shared_tx in
the shared skb data.

The access of the different union elements at several places led to some
confusion about accessing the shared tx_flags e.g. in skb_orphan_try().

    http://marc.info/?l=linux-netdev&m=128084897415886&w=2

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/igb/igb.h b/drivers/net/igb/igb.h
index 6e63d9a..44e0ff1 100644
--- a/drivers/net/igb/igb.h
+++ b/drivers/net/igb/igb.h
@@ -143,7 +143,7 @@
 			u16 next_to_watch;
 			unsigned int bytecount;
 			u16 gso_segs;
-			union skb_shared_tx shtx;
+			u8 tx_flags;
 			u8 mapped_as_page;
 		};
 		/* RX */