[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/net/arcnet/capmode.c b/drivers/net/arcnet/capmode.c
index f6a87bd..cc4610d 100644
--- a/drivers/net/arcnet/capmode.c
+++ b/drivers/net/arcnet/capmode.c
@@ -273,7 +273,8 @@
   /* skb_pull(ackskb, ARC_HDR_SIZE); */
 
 
-  memcpy(ackpkt, lp->outgoing.skb->data, ARC_HDR_SIZE+sizeof(struct arc_cap));
+  skb_copy_from_linear_data(lp->outgoing.skb, ackpkt,
+		ARC_HDR_SIZE + sizeof(struct arc_cap));
   ackpkt->soft.cap.proto=0; /* using protocol 0 for acknowledge */
   ackpkt->soft.cap.mes.ack=acked;