ixgbe: feature - driver to default with FC on.

In the past flow control wasn't enabled by default under the
incorrect assumption that this opened up us to a denial of
service attack.  However since any switch that forwarded flow
control would be extremely msiconfigured and/or buggy, this
concern no longer out weighs the preformance gains from
having FC enabled.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Acked-by: Mallikarjuna R Chilakala <mallikarjuna.chilakala@intel.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ixgbe/ixgbe_main.c

@@ -3169,7 +3169,7 @@ static int __devinit ixgbe_sw_init(struct ixgbe_adapter *adapter)
 #endif
 
 	/* default flow control settings */
-	hw->fc.requested_mode = ixgbe_fc_none;
+	hw->fc.requested_mode = ixgbe_fc_full;
 	hw->fc.high_water = IXGBE_DEFAULT_FCRTH;
 	hw->fc.low_water = IXGBE_DEFAULT_FCRTL;
 	hw->fc.pause_time = IXGBE_DEFAULT_FCPAUSE;