ixgbe: disable tx engine before disabling tx laser

Disabling the tx laser while receiving DMA requests
can hang the device.  After this occurs the device
is in a bad state. The GPIO bit never clears when
PCI master access is disabled and a reboot is required
to get the device in a good state again.

Signed-off-by: John Fastabend <john.r.fastabend@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>