[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/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 0cbfb61..7c467c9 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -40,7 +40,7 @@
 
 	if (skb->len - NR_TRANSPORT_LEN > NR_MAX_PACKET_SIZE) {
 		/* Save a copy of the Transport Header */
-		memcpy(transport, skb->data, NR_TRANSPORT_LEN);
+		skb_copy_from_linear_data(skb, transport, NR_TRANSPORT_LEN);
 		skb_pull(skb, NR_TRANSPORT_LEN);
 
 		frontlen = skb_headroom(skb);
@@ -54,7 +54,7 @@
 			len = (NR_MAX_PACKET_SIZE > skb->len) ? skb->len : NR_MAX_PACKET_SIZE;
 
 			/* Copy the user data */
-			memcpy(skb_put(skbn, len), skb->data, len);
+			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
 			skb_pull(skb, len);
 
 			/* Duplicate the Transport Header */