x86: stop punishing VMs with low priority for TSC timecounter

x86: stop punishing VMs with low priority for TSC timecounter

I suspect that virtualization techniques improved from the time when we
have to effectively disable TSC use in VM.  For instance, it was reported
(complained) in https://github.com/JuliaLang/julia/issues/38877 that
FreeBSD is groundlessly slow on AWS with some loads.

Remove the check and start watching for complaints.

Reviewed by:	emaste, grehan
Discussed with:	cperciva
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D27629