[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/3c505.c b/drivers/net/3c505.c
index c693b5a..e985a85 100644
--- a/drivers/net/3c505.c
+++ b/drivers/net/3c505.c
@@ -1025,7 +1025,7 @@
 	adapter->current_dma.start_time = jiffies;
 
 	if ((unsigned long)(skb->data + nlen) >= MAX_DMA_ADDRESS || nlen != skb->len) {
-		memcpy(adapter->dma_buffer, skb->data, nlen);
+		skb_copy_from_linear_data(skb, adapter->dma_buffer, nlen);
 		memset(adapter->dma_buffer+skb->len, 0, nlen-skb->len);
 		target = isa_virt_to_bus(adapter->dma_buffer);
 	}