ixgbe: fix ring assignment issues for SR-IOV and drop cases

This change fixes the fact that we would trigger a null pointer dereference
or specify the wrong ring if the rings were restored.  This change makes
certain that the DROP queue is a static value, and all other rings are
based on the ring offsets for the PF.

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>