hyperv/et: Make Hyper-V event timer a device.

Submitted by:       Jun Su <junsu microsoft com>
Reviewed by:        sephe, Dexuan Cui <decui microsoft com>
MFC after:  1 week
Sponsored by:       Microsoft OSTC
Differential Revision:      https://reviews.freebsd.org/D5957

hyperv/et: Strip extra white space in function name

Reported by:        Sascha Wildner <saw online de>
MFC after:  1 week
Sponsored by:       Microsoft OSTC