LinuxKPI: Add asm/hypervisor.h header
Sponsored by: Serenity Cyber Security, LLC
Obtained from: OpenBSD
Reviewed by: manu, bz
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D42802
(cherry picked from commit 206e9fea7502dccd126a721c30a1675bdef48633)