ixgbe: remove extra unused queues in DCB + FCoE case

With DCB and FCoE configured extra queues may be allocated and
never used. After this patch we calculate the max correctly.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>