hyperv/stor: Fix print format

Detected by:        PVS Static Analysis
MFC after:  1 week
Sponsored by:       Microsoft OSTC
Differential Revision:      https://reviews.freebsd.org/D5388

hyperv/utils: Code rearrange and cleanup

Split heartbeat, shutdown and timesync out of utils code
and name them properly.

Submitted by:       Jun Su <junsu microsoft com>
Reviewed by:        adrian, sephe, Hongjiang Zhang <honzhan microsoft com>
MFC after:  1 week
Sponsored by:       Microsoft OSTC
Differential Revision:      https://reviews.freebsd.org/D5216

hyperv/vmbus: Use free(9) for interrupt page; it is allocated by malloc(9)

MFC after:  1 week
Sponsored by:       Microsoft OSTC
Differential Revision:      https://reviews.freebsd.org/D5417