[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/irda/vlsi_ir.c b/drivers/net/irda/vlsi_ir.c
index 79b407f..c4be973 100644
--- a/drivers/net/irda/vlsi_ir.c
+++ b/drivers/net/irda/vlsi_ir.c
@@ -993,7 +993,7 @@
 			goto drop;
 		}
 		else
-			memcpy(rd->buf, skb->data, len);
+			skb_copy_from_linear_data(skb, rd->buf, len);
 	}
 
 	rd->skb = skb;			/* remember skb for tx-complete stats */