i40evf: Change a VF mac without reloading the VF driver

Add possibility to change a VF mac address from host side
without reloading the VF driver on the guest side. Without
this patch it is not possible to change the VF mac because
executing i40evf_virtchnl_completion function with
VIRTCHNL_OP_GET_VF_RESOURCES opcode resets the VF mac
address to previous value.

Signed-off-by: Paweł Jabłoński <pawel.jablonski@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>