ixgbe: avoid doing FCoE DDP when adapter is DOWN or RESETTING

There is no point to allow incoming DDP requests from the upper layer stack if
the adapter is going down or being reset.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>