ixgbe: Fix memory leak when SR-IOV VFs are direct assigned

The VF driver had a memory leak that would occur if VFs were assigned to a
guest.  The amount of leak would vary with the number of VFs but could max
out at about 14K per PF.  To reproduce the leak all you would need to do is
enable all the VFs on the first PF.  Then start a loop of loading and
unloading the driver with max_vfs=63 for the first port.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Sibai Li <sibai.li@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>