[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/wan/dscc4.c b/drivers/net/wan/dscc4.c
index 25021a7..dca0244 100644
--- a/drivers/net/wan/dscc4.c
+++ b/drivers/net/wan/dscc4.c
@@ -1904,7 +1904,8 @@
 		struct TxFD *tx_fd = dpriv->tx_fd + last;
 
 		skb->len = DUMMY_SKB_SIZE;
-		memcpy(skb->data, version, strlen(version)%DUMMY_SKB_SIZE);
+		skb_copy_to_linear_data(skb, version,
+					strlen(version) % DUMMY_SKB_SIZE);
 		tx_fd->state = FrameEnd | TO_STATE_TX(DUMMY_SKB_SIZE);
 		tx_fd->data = pci_map_single(dpriv->pci_priv->pdev, skb->data,
 					     DUMMY_SKB_SIZE, PCI_DMA_TODEVICE);