[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>

drivers/net/fec_8xx/fec_main.c

@@ -551,7 +551,9 @@ static int fec_enet_rx_common(struct net_device *dev, int *budget)
 				skbn = dev_alloc_skb(pkt_len + 2);
 				if (skbn != NULL) {
 					skb_reserve(skbn, 2);	/* align IP header */
-					memcpy(skbn->data, skb->data, pkt_len);
+					skb_copy_from_linear_data(skb
+								  skbn->data,
+								  pkt_len);
 					/* swap */
 					skbt = skb;
 					skb = skbn;