MFC 299889,299890,299892

MFC 299889,299890,299892

299889
    hyperv/vmbus: Simplify event processing

    While I'm here, remove useless comment and unnecessary return.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6332

299890
    hyperv/vmbus: Simplify event processing

    For channel0, it will never be processed on event handling path,
    so there is no need to install it.  After skipping in the channel0
    installation, we could discard the channel0 check on event
    handling hot code path.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6333

299892
    hyperv/vmbus: Fix event processing loop indentation.

    No functional changes.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D6334

git-svn-id: svn://svn.freebsd.org/base/stable/10@302107 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f