[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/sun3lance.c b/drivers/net/sun3lance.c
index 327ed79..791e081 100644
--- a/drivers/net/sun3lance.c
+++ b/drivers/net/sun3lance.c
@@ -853,7 +853,7 @@
 
 				skb_reserve( skb, 2 );	/* 16 byte align */
 				skb_put( skb, pkt_len );	/* Make room */
-//			        memcpy( skb->data, PKTBUF_ADDR(head), pkt_len );
+//			        skb_copy_to_linear_data(skb, PKTBUF_ADDR(head), pkt_len);
 				eth_copy_and_sum(skb,
 						 PKTBUF_ADDR(head),
 						 pkt_len, 0);