hyperv/hn: Bring in shims from stable/10

This eases future MFCs to stable/10.

Sponsored by:   Microsoft
Differential Revision:  https://reviews.freebsd.org/D7871

hyperv/hn: Remove the FreeBSD_version check for TSO configuration

It is available on both stable/10 and stable/11. This eases future MFCs
to stable/10.

Sponsored by:   Microsoft
Differential Revision:  https://reviews.freebsd.org/D7872