i40e: only set up the rings to be used

The VSI may be allocated more queues (alloc_queue_pairs) than actually
are to be used (num_queue_pairs), so only allocate rings for the queues
to be used.  The numbers will likely be the same for most VSIs, but can
be different based on how TCs are assigned and enabled.

Change-Id: Ie40f7ad0affbc4b45d6f049bcf02ee2fa24edc74
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Kavindya Deegala <kavindya.s.deegala@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>