[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/net/hamradio/yam.c b/drivers/net/hamradio/yam.c
index ee3ea4f..ac2d6dd 100644
--- a/drivers/net/hamradio/yam.c
+++ b/drivers/net/hamradio/yam.c
@@ -638,7 +638,9 @@
         			dev_kfree_skb_any(skb);
 				break;
 			}
-			memcpy(yp->tx_buf, skb->data + 1, yp->tx_len);
+			skb_copy_from_linear_data_offset(skb->data, 1,
+							 yp->tx_buf,
+							 yp->tx_len);
 			dev_kfree_skb_any(skb);
 			yp->tx_count = 0;
 			yp->tx_crcl = 0x21;