[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>

drivers/isdn/hysdn/hycapi.c

@@ -399,7 +399,8 @@ static u16 hycapi_send_message(struct capi_ctr *ctrl, struct sk_buff *skb)
 			if (_len > 22) {
 				_len2 = _len - 22;
 				skb_copy_from_linear_data(skb, msghead, 22);
-				memcpy(skb->data + _len2, msghead, 22);
+				skb_copy_to_linear_data_offset(skb, _len2,
+							       msghead, 22);
 				skb_pull(skb, _len2);
 				CAPIMSG_SETLEN(skb->data, 22);
 				retval = capilib_data_b3_req(&cinfo->ncci_head,