i40e: Fix a boundary condition and turning off of ntuple

When turning off ntuple with a FD table full situation,
the driver would have auto disabled FD filter additions.
Clear the auto disable flag for FD_SB so that when the
feature is turned on again using "ethtool -K ethx ntuple on"
we can start adding filters once again.

Change-ID: I036a32e7331bcae765b657c8abb4fa070940b163
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>