ixgbevf: Use mac_ops instead of trying to identify NIC type

This change makes it so that we can just use function pointers instead of
having to identify if a given VF is running on a Linux or Windows PF.  By
doing this we can avoid having to pull too much information out of the
lower layers and can instead just make use of the mac_ops pointers since
they should differ between the two types of VFs anyway.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>