ixgbe: fix rx csum return status misinterpretation

the driver was misinterpreting rx_csum return value in the descriptor
so occassionally we would indicate an rx_csum error in our stats
when there was none.  This would have no effect on traffic because
we would just hand the packet to the stack anyway without the offload
flag set, but would increase CPU for those packets that needed a recompute.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/ixgbe/ixgbe_main.c

@@ -420,14 +420,12 @@ static void ixgbe_receive_skb(struct ixgbe_adapter *adapter,
  * @skb: skb currently being received and modified
  **/
 static inline void ixgbe_rx_checksum(struct ixgbe_adapter *adapter,
-					 u32 status_err,
-					 struct sk_buff *skb)
+                                     u32 status_err, struct sk_buff *skb)
 {
 	skb->ip_summed = CHECKSUM_NONE;
 
-	/* Ignore Checksum bit is set, or rx csum disabled */
-	if ((status_err & IXGBE_RXD_STAT_IXSM) ||
-	    !(adapter->flags & IXGBE_FLAG_RX_CSUM_ENABLED))
+	/* Rx csum disabled */
+	if (!(adapter->flags & IXGBE_FLAG_RX_CSUM_ENABLED))
 		return;
 
 	/* if IP and error */