MFC 320490

hyperv/input: Remove unnecessary inclusion.

The unbreaks gcc compilation.

Submitted by: Ryan Libby
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D11415

MFC 316515,316812

316515
hyperv/kbd: Add support for synthetic keyboard.

Synthetic keyboard is the only supported keyboard on GEN2 Hyper-V.

Submitted by: Hongjiang Zhang <honzhan microsoft com>
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D10196

316812
hyperv/kbd: Remove unnecessary assignment.

Reported by: PVS
Sponsored by: Microsoft