[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/net/wanrouter/wanmain.c b/net/wanrouter/wanmain.c
index c49e223..7a19e0e 100644
--- a/net/wanrouter/wanmain.c
+++ b/net/wanrouter/wanmain.c
@@ -277,8 +277,8 @@
 		skb_push(skb, 7);
 		skb->data[0] = 0;
 		skb->data[1] = NLPID_SNAP;
-		memcpy(&skb->data[2], wanrouter_oui_ether,
-		       sizeof(wanrouter_oui_ether));
+		skb_copy_to_linear_data_offset(skb, 2, wanrouter_oui_ether,
+					       sizeof(wanrouter_oui_ether));
 		*((unsigned short*)&skb->data[5]) = htons(type);
 		break;