MFC 321836,321837
321836
hyperv/hn: Renaming and minor cleanup This prepares for the upcoming transparent VF support. Sponsored by: Microsoft Differential Revision: https://reviews.freebsd.org/D11708
321837
hyperv/hn: Add comment about ether_ifattach event subscription. Sponsored by: Microsoft Differential Revision: https://reviews.freebsd.org/D11710