MFC 309310,309311,309316,309318

MFC 309310,309311,309316,309318

309310
    hyperv/hn: Nuke the unused TX taskqueue CPU binding tunable.

    It was an experimental tunable, and is now deemed to be road blocker
    for further changes.  Time to retire it.

    Sponsored by:   Microsoft
    Differential Revision:  https://reviews.freebsd.org/D8654

309311
    hyperv/hn: Allow multiple TX taskqueues.

    Sponsored by:   Microsoft
    Differential Revision:  https://reviews.freebsd.org/D8655

309316
    hyperv/vmbus: Add DEVMETHOD to map cpu to event taskq.

    Sponsored by:   Microsoft
    Differential Revision:  https://reviews.freebsd.org/D8658

309318
    hyperv/hn: Allow TX to share event taskqueues.

    Sponsored by:   Microsoft
    Differential Revision:  https://reviews.freebsd.org/D8659

git-svn-id: svn://svn.freebsd.org/base/stable/10@310768 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f