[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/tokenring/tms380tr.c

@@ -644,7 +644,7 @@ static int tms380tr_hardware_send_packet(struct sk_buff *skb, struct net_device
 		dmabuf  = 0;
 		i 	= tp->TplFree->TPLIndex;
 		buf 	= tp->LocalTxBuffers[i];
-		memcpy(buf, skb->data, length);
+		skb_copy_from_linear_data(skb, buf, length);
 		newbuf 	= ((char *)buf - (char *)tp) + tp->dmabuffer;
 	}
 	else {