[SK_BUFF]: Introduce skb_reset_network_header(skb)

For the common, open coded 'skb->nh.raw = skb->data' operation, so that we can
later turn skb->nh.raw into a offset, reducing the size of struct sk_buff in
64bit land while possibly keeping it as a pointer on 32bit.

This one touches just the most simple case, next will handle the slightly more
"complex" cases.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wan/lmc/lmc_main.c b/drivers/net/wan/lmc/lmc_main.c
index 6d28883..d485146 100644
--- a/drivers/net/wan/lmc/lmc_main.c
+++ b/drivers/net/wan/lmc/lmc_main.c
@@ -1668,7 +1668,7 @@
             skb->protocol = lmc_proto_type(sc, skb);
             skb->protocol = htons(ETH_P_WAN_PPP);
             skb_reset_mac_header(skb);
-//            skb->nh.raw = skb->data;
+            /* skb_reset_network_header(skb); */
             skb->dev = dev;
             lmc_proto_netif(sc, skb);
 
@@ -1706,7 +1706,7 @@
             
             nsb->protocol = lmc_proto_type(sc, skb);
             skb_reset_mac_header(nsb);
-//            nsb->nh.raw = nsb->data;
+            /* skb_reset_network_header(nsb); */
             nsb->dev = dev;
             lmc_proto_netif(sc, nsb);
         }