LinuxKPI: Add static_cpu_has() implementation

static_cpu_has returns true if CPU supports requested feature.

Obtained from: OpenBSD
MFC after: 1 week
Reviewed by: hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33301

(cherry picked from commit f3ddb82d9a99d36ea585d034ccbdea1dfc5b1def)