hyperv/hn: Consolidate hn_{suspend,resume}

Sponsored by:   Microsoft
Differential Revision:  https://reviews.freebsd.org/D8907

hyperv/hn: Function renaming; no functional changes.

Sponsored by:   Microsoft
Differential Revision:  https://reviews.freebsd.org/D8908

hyperv/hn: Factor out function to set rxfilter.

Sponsored by:   Microsoft
Differential Revision:  https://reviews.freebsd.org/D8928