[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/defxx.c b/drivers/net/defxx.c
index 8d29fae..571d82f 100644
--- a/drivers/net/defxx.c
+++ b/drivers/net/defxx.c
@@ -3091,7 +3091,9 @@
 					{
 						/* Receive buffer allocated, pass receive packet up */
 
-						memcpy(skb->data, p_buff + RCV_BUFF_K_PADDING, pkt_len+3);
+						skb_copy_to_linear_data(skb,
+							       p_buff + RCV_BUFF_K_PADDING,
+							       pkt_len + 3);
 					}
 
 					skb_reserve(skb,3);		/* adjust data field so that it points to FC byte */