[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/drivers/isdn/act2000/module.c b/drivers/isdn/act2000/module.c
index e3e5c13..ee2b0b9 100644
--- a/drivers/isdn/act2000/module.c
+++ b/drivers/isdn/act2000/module.c
@@ -442,7 +442,7 @@
 			return 0;
 		}
 		skb_reserve(xmit_skb, 19);
-		memcpy(skb_put(xmit_skb, len), skb->data, len);
+		skb_copy_from_linear_data(skb, skb_put(xmit_skb, len), len);
 	} else {
 		xmit_skb = skb_clone(skb, GFP_ATOMIC);
 		if (!xmit_skb) {