ixgbe: initialize interrupt throttle rate

This commit dropped the setting of the default interrupt throttle rate.

commit 021230d40ae0e6508d6c717b6e0d6d81cd77ac25
Author: Ayyappan Veeraiyan <ayyappan.veeraiyan@intel.com>
Date:   Mon Mar 3 15:03:45 2008 -0800

    ixgbe: Introduce MSI-X queue vector code

The following patch adds it back.  Without this the default value of 0
causes the performance of this card to be awful.  Restoring these to the
default values yields much better performance.

This regression has been around since 2.6.25.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
CC: stable@kernel.org [2.6.25 and later]
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/ixgbe/ixgbe_main.c

@@ -2303,6 +2303,12 @@ static int __devinit ixgbe_set_interrupt_capability(struct ixgbe_adapter
 	int err = 0;
 	int vector, v_budget;
 
+	/*
+	 * Set the default interrupt throttle rate.
+	 */
+	adapter->rx_eitr = (1000000 / IXGBE_DEFAULT_ITR_RX_USECS);
+	adapter->tx_eitr = (1000000 / IXGBE_DEFAULT_ITR_TX_USECS);
+
 	/*
 	 * It's easy to be greedy for MSI-X vectors, but it really
 	 * doesn't do us much good if we have a lot more vectors