[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/s390/net/netiucv.c b/drivers/s390/net/netiucv.c
index cd42bd5..e10e85e 100644
--- a/drivers/s390/net/netiucv.c
+++ b/drivers/s390/net/netiucv.c
@@ -645,7 +645,8 @@
 			privptr->stats.rx_dropped++;
 			return;
 		}
-		memcpy(skb_put(skb, pskb->len), pskb->data, pskb->len);
+		skb_copy_from_linear_data(pskb, skb_put(skb, pskb->len),
+					  pskb->len);
 		skb_reset_mac_header(skb);
 		skb->dev = pskb->dev;
 		skb->protocol = pskb->protocol;
@@ -744,7 +745,9 @@
 		header.next = conn->tx_buff->len + skb->len + NETIUCV_HDRLEN;
 		memcpy(skb_put(conn->tx_buff, NETIUCV_HDRLEN), &header,
 		       NETIUCV_HDRLEN);
-		memcpy(skb_put(conn->tx_buff, skb->len), skb->data, skb->len);
+		skb_copy_from_linear_data(skb,
+					  skb_put(conn->tx_buff, skb->len),
+					  skb->len);
 		txbytes += skb->len;
 		txpackets++;
 		stat_maxcq++;