MFC 295875,295876,295877,295916,295918

MFC 295875,295876,295877,295916,295918

295875
    hyperv/hn: Rename TX related function and struct fields a bit

    Preamble to implement the ifnet.if_transmit method.

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5344

295876
    hyperv/hn: Staticize and rename packet TX done function

    It is only used in hv_netvsc_drv_freebsd.c; and rename it to hn_tx_done()
    mainly to reserve "xmit" for ifnet.if_transmit implement.

    While I'm here, remove unapplied comment.

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5345

295877
    hyperv/hn: Add TX method for txeof processing.

    Preamble to implement ifnet.if_transmit method.

    Reviewed by:        adrian
    Approved by:        adrian (mentor)
    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5346

295916
    hyperv/hn: Factor out hn_send_pkt() from hn_start_locked()

    It will be shared w/ the upcoming ifnet.if_transmit method
    implementation.

    No functional change.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5385

295918
    hyperv/hn: Use IFQ_DRV_PREPEND instead of IF_PREPEND

    IF_PREPEND promises out-of-order packet sending when the TX desc list
    is depleted. It was overlooked and copied blindly when the transmission
    path was partially rewritten.

    MFC after:  1 week
    Sponsored by:       Microsoft OSTC
    Differential Revision:      https://reviews.freebsd.org/D5386

git-svn-id: svn://svn.freebsd.org/base/stable/10@301864 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f