[SK_BUFF]: Introduce skb_copy_from_linear_data{_offset}

To clearly state the intent of copying from 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@redhat.com>
diff --git a/drivers/atm/atmtcp.c b/drivers/atm/atmtcp.c
index fc518d8..1b9493a 100644
--- a/drivers/atm/atmtcp.c
+++ b/drivers/atm/atmtcp.c
@@ -221,7 +221,7 @@
 	hdr->vpi = htons(vcc->vpi);
 	hdr->vci = htons(vcc->vci);
 	hdr->length = htonl(skb->len);
-	memcpy(skb_put(new_skb,skb->len),skb->data,skb->len);
+	skb_copy_from_linear_data(skb, skb_put(new_skb, skb->len), skb->len);
 	if (vcc->pop) vcc->pop(vcc,skb);
 	else dev_kfree_skb(skb);
 	out_vcc->push(out_vcc,new_skb);
@@ -310,7 +310,7 @@
 		goto done;
 	}
 	__net_timestamp(new_skb);
-	memcpy(skb_put(new_skb,skb->len),skb->data,skb->len);
+	skb_copy_from_linear_data(skb, skb_put(new_skb, skb->len), skb->len);
 	out_vcc->push(out_vcc,new_skb);
 	atomic_inc(&vcc->stats->tx);
 	atomic_inc(&out_vcc->stats->rx);