If the VF sends a MACVLAN request with index of zero then it is not
actually trying to add a filter.  Check the index value and only
indicate that operation is not allowed when the VF is actually trying
to add a filter.
Signed-off-by: NGreg Rose <gregory.v.rose@intel.com>
Tested-by: NSibai Li <sibai.li@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>