MFC 301483,301484,301487,301488,301583,301588

MFC 301483,301484,301487,301488,301583,301588

301483
    hyperv: Move machine dependent bits into machine dependent files.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6701

301484
    hyperv/vmbus: Define type for channel messages.

    And fix message processing; only channel messages are supported.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6706

301487
    hyperv/vmbus: Factor out channel message processing

    This paves the way for further cleanup.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6707

301488
    hyperv/vmbus: Constify channel message

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6708

301583
    hyperv/vmbus: Busdma-fy MNF and event flags.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6744

301588
    hyperv/vmbus: Change tx_evtflags type to u_long to match vmbus_evtflags

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6745

git-svn-id: svn://svn.freebsd.org/base/stable/10@302170 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f