[SK_BUFF]: unions of just one member don't get anything done, kill them

Renaming skb->h to skb->transport_header, skb->nh to skb->network_header and
skb->mac to skb->mac_header, to match the names of the associated helpers
(skb[_[re]set]_{transport,network,mac}_header).

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e6a9e45..f49afaa 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -828,7 +828,7 @@
 		old_iph = ip_hdr(skb);
 	}
 
-	skb->h.raw = skb->nh.raw;
+	skb->transport_header = skb->network_header;
 	skb_push(skb, gre_hlen);
 	skb_reset_network_header(skb);
 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));