[SK_BUFF]: Introduce skb_copy_to_linear_data{_offset}

To clearly state the intent of copying to linear sk_buffs, _offset being a
overly long variant but interesting for the sake of saving some bytes.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
diff --git a/drivers/s390/net/qeth_main.c b/drivers/s390/net/qeth_main.c
index df7f279..ad7792d 100644
--- a/drivers/s390/net/qeth_main.c
+++ b/drivers/s390/net/qeth_main.c
@@ -2501,7 +2501,8 @@
 			vlan_tag = qeth_rebuild_skb(card, skb, hdr);
 		else { /*in case of OSN*/
 			skb_push(skb, sizeof(struct qeth_hdr));
-			memcpy(skb->data, hdr, sizeof(struct qeth_hdr));
+			skb_copy_to_linear_data(skb, hdr,
+						sizeof(struct qeth_hdr));
 		}
 		/* is device UP ? */
 		if (!(card->dev->flags & IFF_UP)){
@@ -3870,9 +3871,9 @@
 		 * memcpys instead of one memmove to save cycles.
 		 */
 		skb_push(skb, VLAN_HLEN);
-		memcpy(skb->data, skb->data + 4, 4);
-		memcpy(skb->data + 4, skb->data + 8, 4);
-		memcpy(skb->data + 8, skb->data + 12, 4);
+		skb_copy_to_linear_data(skb, skb->data + 4, 4);
+		skb_copy_to_linear_data_offset(skb, 4, skb->data + 8, 4);
+		skb_copy_to_linear_data_offset(skb, 8, skb->data + 12, 4);
 		tag = (u16 *)(skb->data + 12);
 		/*
 		 * first two bytes  = ETH_P_8021Q (0x8100)