[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/net/irda/au1k_ir.c b/drivers/net/irda/au1k_ir.c
index cdd1f6c..4dbdfaa 100644
--- a/drivers/net/irda/au1k_ir.c
+++ b/drivers/net/irda/au1k_ir.c
@@ -604,7 +604,7 @@
 				skb_put(skb, count);
 			else
 				skb_put(skb, count-2);
-			memcpy(skb->data, (void *)pDB->vaddr, count-2);
+			skb_copy_to_linear_data(skb, pDB->vaddr, count - 2);
 			skb->dev = dev;
 			skb_reset_mac_header(skb);
 			skb->protocol = htons(ETH_P_IRDA);