ixgbe: fix panic when shutting down system with WoL enabled

This patch added to 2.6.34:

	commit 5f6c0181
	Author: Jesse Brandeburg <jesse.brandeburg@intel.com>
	Date:   Wed Apr 14 16:04:23 2010 -0700

	    ixgbe: fix bug with vlan strip in promsic mode

among other things added a function called ixgbe_vlan_filter_enable.
This new function wants to access and set some rx_ring parameters, but
adapter->rx_ring has already been freed.  This simply moves the free
until after the access and makes __ixgbe_shutdown look more like
ixgbe_remove.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>