[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/sungem.c b/drivers/net/sungem.c
index 4bb89dec..9df1038 100644
--- a/drivers/net/sungem.c
+++ b/drivers/net/sungem.c
@@ -848,7 +848,7 @@
 			skb_reserve(copy_skb, 2);
 			skb_put(copy_skb, len);
 			pci_dma_sync_single_for_cpu(gp->pdev, dma_addr, len, PCI_DMA_FROMDEVICE);
-			memcpy(copy_skb->data, skb->data, len);
+			skb_copy_from_linear_data(skb, copy_skb->data, len);
 			pci_dma_sync_single_for_device(gp->pdev, dma_addr, len, PCI_DMA_FROMDEVICE);
 
 			/* We'll reuse the original ring buffer. */