[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/au1k_ir.c b/drivers/net/irda/au1k_ir.c
index 27afd0f..cdd1f6c 100644
--- a/drivers/net/irda/au1k_ir.c
+++ b/drivers/net/irda/au1k_ir.c
@@ -526,7 +526,7 @@
 	
 	if (aup->speed == 4000000) {
 		/* FIR */
-		memcpy((void *)pDB->vaddr, skb->data, skb->len);
+		skb_copy_from_linear_data(skb, pDB->vaddr, skb->len);
 		ptxd->count_0 = skb->len & 0xff;
 		ptxd->count_1 = (skb->len >> 8) & 0xff;