ixgbe: fix X540 ethtool loopback test.

On X540 we need to set the MACC.FLU bit to 1 in order to force the link
up before entering MAC loopback.  This is only used in the ethtool loopback
test, which was failing.  This patch corrects it.
Signed-off-by: NDon Skidmore <donald.c.skidmore@intel.com>
Tested-by: NEvan Swanson <evan.swanson@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ixgbe/ixgbe_ethtool.c

@@ -1595,6 +1595,13 @@ static int ixgbe_setup_loopback_test(struct ixgbe_adapter *adapter)
 	struct ixgbe_hw *hw = &adapter->hw;
 	u32 reg_data;
 
+	/* X540 needs to set the MACC.FLU bit to force link up */
+	if (adapter->hw.mac.type == ixgbe_mac_X540) {
+		reg_data = IXGBE_READ_REG(&adapter->hw, IXGBE_MACC);
+		reg_data |= IXGBE_MACC_FLU;
+		IXGBE_WRITE_REG(&adapter->hw, IXGBE_MACC, reg_data);
+	}
+
 	/* right now we only support MAC loopback in the driver */
 	reg_data = IXGBE_READ_REG(&adapter->hw, IXGBE_HLREG0);
 	/* Setup MAC loopback */