i40e: Allow VF to set already assigned MAC address

The VF is allowed to request the PF to set its already assigned
MAC address without generating an error.

Change-Id: I8dfdf353396995dbbb26cafab4e42b451911da3d
Signed-off-by: Greg Rose <gregory.v.rose@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>