i40e/i40evf: Use correct number of VF vectors

Now that the 2.4 firmware reports the correct number of MSI-X vectors,
use this value correctly when communicating with the VF, and when
setting up the interrupt linked list.

The PF has always reported the correct number of MSI-X vectors, so we
should never increment the value in the vf driver.

Change-ID: Ifeefc631c321390192219ce2af9ada6180c1492f
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>