i40e: limit lan queue count in large CPU count machine

When a machine has more CPUs than queue pairs, e.g. 512 cores, the
counting gets a little funky and turns off Flow Director with the
message:
  not enough queues for Flow Director. Flow Director feature is disabled

This patch limits the number of lan queues initially allocated to
be sure we have some left for FD and other features.

Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>