libertas: Don't claim to have checksummed incoming packets.

This explains why we never noticed the corruption of checksums on
outgoing packets... we weren't actually checking them either.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/rx.c

@@ -147,7 +147,7 @@ void lbs_upload_rx_packet(struct lbs_private *priv, struct sk_buff *skb)
 		else
 			skb->protocol = eth_type_trans(skb, priv->dev);
 	}
-	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	skb->ip_summed = CHECKSUM_NONE;
 	netif_rx(skb);
 }