[SK_BUFF]: Introduce skb_reset_mac_header(skb)

For the common, open coded 'skb->mac.raw = skb->data' operation, so that we can
later turn skb->mac.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/s390/net/ctcmain.c b/drivers/s390/net/ctcmain.c
index 0d6d5fc..787c013 100644
--- a/drivers/s390/net/ctcmain.c
+++ b/drivers/s390/net/ctcmain.c
@@ -455,7 +455,7 @@
 			return;
 		}
 		skb_put(pskb, header->length);
-		pskb->mac.raw = pskb->data;
+		skb_reset_mac_header(pskb);
 		len -= header->length;
 		skb = dev_alloc_skb(pskb->len);
 		if (!skb) {
@@ -473,7 +473,7 @@
 			return;
 		}
 		memcpy(skb_put(skb, pskb->len), pskb->data, pskb->len);
-		skb->mac.raw = skb->data;
+		skb_reset_mac_header(skb);
 		skb->dev = pskb->dev;
 		skb->protocol = pskb->protocol;
 		pskb->ip_summed = CHECKSUM_UNNECESSARY;
diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c
index 594320c..82edf20 100644
--- a/drivers/s390/net/netiucv.c
+++ b/drivers/s390/net/netiucv.c
@@ -635,7 +635,7 @@
 			return;
 		}
 		skb_put(pskb, header->next);
-		pskb->mac.raw = pskb->data;
+		skb_reset_mac_header(pskb);
 		skb = dev_alloc_skb(pskb->len);
 		if (!skb) {
 			PRINT_WARN("%s Out of memory in netiucv_unpack_skb\n",
@@ -646,7 +646,7 @@
 			return;
 		}
 		memcpy(skb_put(skb, pskb->len), pskb->data, pskb->len);
-		skb->mac.raw = skb->data;
+		skb_reset_mac_header(skb);
 		skb->dev = pskb->dev;
 		skb->protocol = pskb->protocol;
 		pskb->ip_summed = CHECKSUM_UNNECESSARY;
diff --git a/drivers/s390/net/qeth_eddp.c b/drivers/s390/net/qeth_eddp.c
index 7c735e1..910a8ab 100644
--- a/drivers/s390/net/qeth_eddp.c
+++ b/drivers/s390/net/qeth_eddp.c
@@ -486,7 +486,7 @@
 		return -ENOMEM;
 	}
 	if (qhdr->hdr.l2.id == QETH_HEADER_TYPE_LAYER2) {
-		skb->mac.raw = (skb->data) + sizeof(struct qeth_hdr);
+		skb->mac.raw = skb->data + sizeof(struct qeth_hdr);
 		memcpy(&eddp->mac, eth_hdr(skb), ETH_HLEN);
 #ifdef CONFIG_QETH_VLAN
 		if (eddp->mac.h_proto == __constant_htons(ETH_P_8021Q)) {
diff --git a/drivers/s390/net/qeth_main.c b/drivers/s390/net/qeth_main.c
index d502b77..2882202 100644
--- a/drivers/s390/net/qeth_main.c
+++ b/drivers/s390/net/qeth_main.c
@@ -2278,7 +2278,7 @@
 	    (card->info.link_type == QETH_LINK_TYPE_LANE_TR))
 	 	return tr_type_trans(skb,dev);
 #endif /* CONFIG_TR */
-	skb->mac.raw = skb->data;
+	skb_reset_mac_header(skb);
 	skb_pull(skb, ETH_HLEN );
 	eth = eth_hdr(skb);
 
@@ -2461,7 +2461,7 @@
 	if (card->options.fake_ll)
 		qeth_rebuild_skb_fake_ll(card, skb, hdr);
 	else
-		skb->mac.raw = skb->data;
+		skb_reset_mac_header(skb);
 	skb->ip_summed = card->options.checksum_type;
 	if (card->options.checksum_type == HW_CHECKSUMMING){
 		if ( (hdr->hdr.l3.ext_flags &