hyperv: Use standard taskqueue instead of hv_work_queue

HyperV code was ported from Linux. There is an implementation of
work queue called hv_work_queue. In FreeBSD, taskqueue could be
used for the same purpose. Convert all the consumer of hv_work_queue
to use taskqueue, and remove work queue implementation.

Submitted by: Jun Su <junsu microsoft com>
Reviewed by: adrian, Hongjiang Zhang <honzhan microsoft com>
Approved by: adrian (mentor)
MFC after: 1 week
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D4963