ixgbe: Correct handling of any outer UDP checksum setting

BugLink: http://bugs.launchpad.net/bugs/1536473

If an outer UDP checksum is set, pass the skb up with CHECKSUM_NONE
so that the stack will check the checksum. Do not increment an
error counter, because we don't know that there is an actual error.
Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit d469251b)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -1483,7 +1483,7 @@ static inline void ixgbe_rx_checksum(struct ixgbe_ring *ring,
 			return;
 
 		if (ixgbe_test_staterr(rx_desc, IXGBE_RXDADV_ERR_OUTERIPER)) {
-			ring->rx_stats.csum_err++;
+			skb->ip_summed = CHECKSUM_NONE;
 			return;
 		}
 		/* If we checked the outer header let the stack know */