[SK_BUFF]: Introduce skb_mac_header()

For the places where we need a pointer to the mac header, it is still legal to
touch skb->mac.raw directly if just adding to, subtracting from or setting it
to another layer header.

This one also converts some more cases to skb_reset_mac_header() that my
regex missed as it had no spaces before nor after '=', ugh.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 2fcaf5b..560560f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1232,7 +1232,7 @@
 	}
 	rcu_read_unlock();
 
-	__skb_push(skb, skb->data - skb->mac.raw);
+	__skb_push(skb, skb->data - skb_mac_header(skb));
 
 	return segs;
 }