ixgbe: fix flags relating to perfect filters to support coexistence

I am removing the requirement that Ntuple filters have the same
number of queues and requirements as ATR.  As a result this change will
make it so that all the Ntuple flag does is disable ATR for now.

This change fixes an issue in which we were incorrectly re-enabling ATR
when we exited perfect filter mode.  This was due to the fact that the
logic assumed RSS and DCB were mutually exclusive which is no longer the
case.

To correct this we just need to add a check to guarantee DCB is disabled
before re-enabling ATR.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>