[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/smsc-ircc2.c b/drivers/net/irda/smsc-ircc2.c
index e845386..198bf3b 100644
--- a/drivers/net/irda/smsc-ircc2.c
+++ b/drivers/net/irda/smsc-ircc2.c
@@ -1162,7 +1162,7 @@
 		self->new_speed = speed;
 	}
 
-	memcpy(self->tx_buff.head, skb->data, skb->len);
+	skb_copy_from_linear_data(skb, self->tx_buff.head, skb->len);
 
 	self->tx_buff.len = skb->len;
 	self->tx_buff.data = self->tx_buff.head;