i40e: Add condition to enter fdir flush and reinit

When FD_SB/ATR are not enabled, do not allow flow director flush
and reinit.

Change-ID: Iafe261c1862992981615815551abd1ed9fada0a8
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Signed-off-by: Patrick Lu <patrick.lu@intel.com>
Tested-by:  <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>