[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/skfp/skfddi.c b/drivers/net/skfp/skfddi.c
index 064e7c2..a7ef6c8 100644
--- a/drivers/net/skfp/skfddi.c
+++ b/drivers/net/skfp/skfddi.c
@@ -1937,7 +1937,7 @@
 	}
 	skb_reserve(skb, 3);
 	skb_put(skb, len);
-	memcpy(skb->data, look_ahead, len);
+	skb_copy_to_linear_data(skb, look_ahead, len);
 
 	// deliver frame to system
 	skb->protocol = fddi_type_trans(skb, smc->os.dev);