[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>

net/ipv6/xfrm6_mode_tunnel.c

@@ -108,9 +108,9 @@ static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)
 			ip6ip_ecn_decapsulate(skb);
 		skb->protocol = htons(ETH_P_IP);
 	}
-	old_mac = skb->mac.raw;
+	old_mac = skb_mac_header(skb);
 	skb_set_mac_header(skb, -skb->mac_len);
-	memmove(skb->mac.raw, old_mac, skb->mac_len);
+	memmove(skb_mac_header(skb), old_mac, skb->mac_len);
 	skb->nh.raw = skb->data;
 	err = 0;